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MANUALS 


Students   of  Medicine 


HIS  T'©*'®'&«. 


BY 

E.    KLEIN,    M.D.,    F.R.S. 

LECTURER     ON     GENERAL     ANATOMY     AND      PHYSIOLOGY 
AND 

J.    S.    EDKINS,    M.A.,    MB. 

JOINT    LECTURER   AND    DEMONSTRATOR    OF    PHYSIOLOGY    IN    THE    MEDICAL 
SCHOOL   OF   ST.    BARTHOLOMEW'S   HOSPITAL,    LONDON 


WITH  296  ILLUSTRATIONS 


REVISED      AND      ENLARGED      EDITION 


LEA     BROTHERS     &    CO., 

PHILADELPHIA     AND     NEW     YORK, 


Co  tl&f  fHfmorg 

OF 

SIR   WILLIAM    BOWMAN,    LL.D.,    F.R.S., 

THIS  BOOK  IS   DEDICATED, 

IN  ACKNOWLEDGMENT  OP   HIS  MANY  AND  GREAT   DISCOVERIES 

IN   ANATOMY   AND   PHYSIOLOGY. 


PREFACE    TO    THE 
REVISED     AND    ENLARGED    EDITION. 


Since  the  last  edition  of  this  book  in  1889,  consider- 
able additions  have  been  made  to  the  knowledge  of 
minute  structural  anatomy.  The  progress  in  the 
knowledge  of  the  structure  and  life  of  the  cell  and 
nucleus,  the  remarkable  discoveries  in  the  structure 
of  the  central  nervous  system  and  sense  organs 
— introduced  bv  the  method  of  Golo-i,  and  followed 
up  by  the  brilliant  work  of  Ramon  y  Cajal,  Kolliker, 
Lenhossek,  Retzius,  and  others — have  made  it  neces- 
sary to  revise  and  to  make  considerable  additions 
to  the  chapters  dealing  with  these  organs.  While 
care  has  been  taken  to  correct  and  amplify  other 
jmrts  of  the  book,  the  chapters  on  the  central  nervous 
system  have  been  practically  rewritten. 

The  task  of  rewriting  and  re-editing  the  chapters 
on  the  brain  and  medulhx  and  on  the  alimentarv 
canal  has  devolved  upon  my  colleague  Dr.  Edkins, 
who  is  now  associated  with  me  as  joint-author. 

While  a  large  number  of  the  illustrations  of  the 
former  edition  have  been  retained,  a  considerable 
number  has  been  added  ;  these  are  either  original 
photograms  prepared  by  Mr.  Norman  from  Dr. 
Edkins's  and  my  own  speciiiiens,  or  they  are  copied 
from  Kolliker's  "  Handbuch,"  from  Ramon  y  Cajal, 
from  Schiifer  (Quain's  "  Anatomy "),  from  Halli- 
burton (Kirke's  "  Physiology  "),  and  from  Klein  and 
Noble  Smith's  "  Atlas  of  Histoloijv."  To  our  colleague 
Dr.  Tooth  our  special  thanks  are  due  for  the  loan  of 
some  of  the  lantern  slides  illustrating  the  medulla. 

E.    KLEIN. 

St,  B.uiTHOLOMEw's  Hospital, 
LONDOX.  — 1S98. 


COXTENTS. 


CHAPTER 

I.— Cells  .  ,  .  .  . 

II.— Blood 

III. — Epithelium         .... 
IV. — Endothelium     .... 
V, — Fibrous  Connective  Tissues 

VI. — Cartilage 

VII.- Bone 

VIII. — Xon-strii:)ed  Muscular  Tissue     . 
IX. — fStriped  Muscular  Tissue   . 
X.— The  Heart  and  Blood-Vessels    . 
XI. — The  Lymjjhatic  Vessels 
XII. — Follicles  or  Simple  Lymph  Glands 
XIII.— Compound  Lymphatic  Glands  . 
XIV. — Nerve  Fibres      .... 
XV. — Peripheral  Xerve-Endings 
XVI.— The  Spinal  Cord 

XVII.— The  Medulla  Oblongata  or  Spinal  Bulb 
XVJII. — Continuation  of  the  Medulla  Oblongata  throu^ 
Pons  Varolii  and  the  Region  of  the  Crura 
XIX. — The  Cerebrum  and  Cerebellum 
XX. — The  Cerebro-Spinal  Ganglia 
XXI. — The  Sympathetic  System 
XXII. — General  Considerations  as  to  the  Anatomical  Con 
stitution  and  Nature  of  the  Nervous  System 

XXIII.  -The  Teeth 

XXIV.— The  Salivary  Glands 

XXV.— The  Moutli.  Pharynx,  and  Tongue   . 
XXVI. — The  (Esophagus  and  Stomach   .... 


h  the 


PAGE 

1 

19 

30 

40 

46 

63 

68 

86 

90 

10.5 

117 

126 

134 

140 

155 

170 

202 

216 
235 
253 

2.58 

268 
275 
286 
298 
307 


xu 


Elements  of  Histology. 


. "     CHAPTJER  PAOE 

XKVIL— The  Small  and  Large  Intestine  ....  317 

XXTIIL  — The  Glands  of -Brunner  andthe  Pancreas  .         .  328 

XXIX.— The  Liver 333 

XXX.— The  Organs  of  Respiration 3.30 

XXXI.— The  Spleen 3-51 

XXXII.— The  Kidney.  L'reter  and  Bladder                          .  356 

XXXIIL— The  Male  Genital  Organs 372 

XXXIV.— The  Female  Genital  Organs         .         .         .         .386 

XXXV.— The  Mammary  Gland 400 

XXXVI.— The  Skin 404 

XXXVII.— The  Coniuuctiva  and  its  Glands  .         .         .424 

XXXVIII.  — Cornea,     Sclerotic,     Ligamentum     Pectinatnrn 

and  Ciliary  Muscle 429 

XXXIX. — Iris,  Ciliary  Processes  and  Choroid                       .  436 

XL.-— The  Lens  and  Vitreous  Body       ...  442 

XLI.  -The  Retina 44.5 

XLIL— The  Outer  and  Middle  Ear           ....  4-58 

XLIIL— The  Internal  Ear         .        .             \.        .  460 

XLIV. — The  Xasal  Mucous  Membrane     ....  47-") 

XLV.— The  Ductless  Glands 484 


jprnpfrtn  o(  l\ft 

^sjuciaiimi  uf  i^e  ^^lumni  of  t^e 

CoUtgc  of  I^DS.  &  iurgs..  gfto  fork, 

Elements  of  Histology. 


CHAPTER    I. 


CELLS. 


1.  The  ripe  oviiiii  (Fig.  1)  of  man  and  mammals 
is  a  minute  spherical  mass  of  a  soft,  gelatinous,  trans- 
parent, granular-looking  substance,  containing  nume- 
rous minute  particles — yolk 
globules.  It  is  invested  by 
a  radially  striated  delicate 
membrane  called  the  zona 
pellucida.  Inside  this  mass, 
and  situated  more  or  less 
excentrically,  is  a  vesicle — 
the  germinal  vesicle  —  and 
inside  this,  one  or  more 
solid  spots  —  the  germinal 
spot  or  spots.  The  gela- 
tinous transparent  substance 
of    the    ovum,    containing    a 

very  large  percentage  of  proteid  material,  is  called 
protoplasm.  Before  and  immediately  after  fertilisa- 
tion, the  protoplasm  of  the  ovum  shoAv^s  distinct 
movement,  consisting  in  contraction  and  expansion. 
These  movements  are  spontaneous — i.e.  not  caused 
by  any  directly  visible  external  influence. 

The  diameter  of  the  ripe  ovum  in  man  and  do- 
mestic animals  varies  between  ^^^  and  y^^  of  an 
inch.     But  before  it  ripens  the  ovum  is  considerably 


V--^-c 


Fig.  1. — Ripe  Ovum  of  Cat. 

a,  Zona  pellucida ;   h,   gerniinal 
vesicle;  c,  protoplasm. 


2  Elements  of  Histology. 

smaller — in    fact,    its    size    is    in     proportion    to    its 
state  of  develo])ment. 

2.   Fertilisation  causes   marked  changes  in  the 
contractions  of  the  protoplasm  of  the  ovum  ;    these 


Fig.  2.— From  a  Section  through  the  Blastoderm  of  Chick,  unincubated. 

a  Cells  foimiui,'  ilie  ectoderm  ;  b,  cells  forming  the  endoaerm  ;  c,  larue 

formative  cells ;  /,  segmentation  cavity.    {Handooolc.) 

lead  to  cleavage  or  division  of  its  body  into  two  jiarts, 
the  germinal  vesicle  having  previously  split  up  into 
two  bodies  or  nuclei ;  so  that  we  now  find  the  ovum 

/ 


Fig.  3.— From  a  Section  through  the  Rudiment  of  the  Embryo  Chick, 


e,  rrimitive  groove ;  /,  dorsal  laminae  of  epihlast :  d,  raesoblast.     The 
thin  layer  of  spindle-shaped  cells  is  the  hypoblast.    (.Handbook.) 

has  originated  two  new  elements,  each  of  which 
consists  of  protoplasm,  of  the  same  substance  as  that 
of  the  original  ovum,  and  each  contains  one  nucleus 
or  kernel. ;    The   investment    of  the    ovum  rakes   no 


Cells, 


part  ill  this  process  of  division.      Not  long  afterwards, 
each  of  the  two  daughter  elements  undergoes  cleavage 


Fig.  4.— Vertical  Section  tlirough  the  Ovum  of  Bufo  Cinereiis,  in  the  early 
stage  of  the  Embryo  Development. 

a,  Tegmental  layer  of  epiblast ;  6,  dorsal  groove ;  c,  rudiiuent  of  central  nervous 
system  ;  d,  notochord  ;  e,  deep  layer  of  epiblast ;  /,  mesoblast ;  g,  hypoblast ; 
ft,  cavity  of  alimentary  canal— Rusconi's  cavity  ;  h,  central  yolk  ;  A:,  remainder 
of  von  Baer's  or  segmentation  cavity.    ^Handbook.) 

or  division  into  two  new  elements,  the  nucleus  having 
previously  divided  into  two,  so  that  each  new 
offspring  possesses  its  own  nucleus.  This  process 
of    division  is   continued    in    the    same    manner    for 


4  Elements  of  Histology. 

many  generations  (Figs.  2,  3,  4),  so  that  after  a 
few  davs  we  find  within  the  orioinal  investment  of 
the  ovum  a  large  number  of  minute  elements,  each 
consisting  of  protoplasm,  and  each  containing  a 
nucleus. 

3.  From  these  elements,  which  become  smaller  as 
the  process  of  cleavage  progresses,  all  parts  and  organs 
of  the  embryo  and  its  membranes  are  formed.  It  can 
be  easily  shown  that  the  individual  elements  possess 
the  power  of  contractility.  Either  spontaneously  or 
under  the  influence  of  moderate  heat,  electricity, 
mechanical  or  chemical  stimulation,  they  throw  out 
processes  and  withdraw  them  again,  their  substance 
flowing  slowly  but  perceptibly  along.  Hence  they 
can  change  their  position.  In  this  respect  they  com- 
pletely resemble  those  lowest  organisms  which  are 
known  as  amceb?e,  each  of  these  being  likewise  a 
nucleated  mass  of  protoplasm.  Wherefore  this  move- 
ment is  termed  amoeboid  movement.  It  can  be  further 
shown  that  they,  like  amoeb?e,  grow  in  size  and  divide 
■ — that  is  to  say,  the  individuals  of  a  generation  grow 
in  size  l^efore  each  gives  rise  to  two  new  daughter 
individuals. 

4.  Although  for  some  time  during  embryonic  life 
the  elements  constituting  the  organs  of  the  embryo  are 
possessed  of  these  characters,  a  time  arrives  when 
only  a  limited  number  of  them  retain  the  power  of 
contractility  in  any  marked  degree.  At  birth  only  the 
white  corpuscles  of  the  blood  and  lymph,  many  of  the 
elements  of  the  lymphatic  organs,  and  the  muscular 
tissues,  possess  this  power;  while  the  others  lose  it, 
or  at  any  rate  do  not  show  it  except  when  dividing 
into  two  new  elements.  Some  of  these  elements 
retain  their  protoplasmic  basis ;  as  a  rule,  each  con- 
tains one  nucleus  (but  some  two  or  more),  and  is 
capable  of  giving  origin  by  division  to  a  new  genera- 
tion.  Others,  however,  change  their  nature  altogether, 


Cells.  5 

their  protoplasm  and  nucleus  disappear,  and  tliey 
give  origin  to  material  other  than  protopLism — e.g. 
collagenous,  osseous,  elastic,  and  other  suljstances. 
As  develojiment  proceeds,  and  after  birth  of  the 
fa3tus,  different  cells  assume  different  functions,  which 
for  each  kind  are  of  a  special  character  and  constitute 
its  specific  character  or  its  specific  junction. 

5.  Beginning  with  the  ovum,  and  ending  with  the 
protoplasmic  nucleated  elements  found  constituting 
the  organs  and  tissues  of  the  embryo  and  adult,  we 
have,  then,  one  uninterrupted  series  of  generations  of 


Fig.  5. — Amoeboid  iiioveinent  of  a  Wliite  Blood  Corpuscle  of  Man  ;  various 
phases  of  nioveiiient.     (Handbook.) 

elements,  which  with  Schwann  we  call  cells  and  with 
Briicke  elementary  organisms.  Of  these  it  can  be  said 
that  not  only  is  each  of  them  derived  from  a  cell 
(Virchow  :  omnis  cellula  a  cellula),  but  each  consists 
of  the  protoplasm  of  Max  Schultze  (sarcode  of  Dujar- 
din),  is  without  any  investing  membrane,  and  includes 
generally  one  nucleus,  but  may  contain  two  or  more. 
We  can  further  say  that  each  of  these  cells  shows  the 
phenomenon  of  growth,  which  presupposes  nutrition 
and  reproduction.  A.11  of  them  in  an  early  stage  of 
their  life-history,  and  some  of  them  throughout  it,  show 
the  phenomenon  of  contractility,  or  amoeboid  move- 
ment (Fig.  5). 

In  a  recent  work,  and  following  the  procedure  of 
V.  Sachs  on  the  life  and  activity  of  vegetable  cells,  v. 
KoUiker  systematises  and  summarises  those  of  animal 
cells  thus  :  The   protoplasm  and  nucleus  constituting 


6  Elements  of  Histology. 

a  vegetable  cell  is  called  by  v.  Sachs  an  energid;  in 
the  animal  body  it  is  represented  by  a  nucleated 
protoplasmic  cell  without  a  cellulose  membrane,  and 
is  called  by  v.  Kolliker  a  protohlast  (germinal  matter 
of  Beale).  All  protoblasts,  as  also  all  energids,  are 
always  derived  from  parent  protoblasts ;  they  always 
propagate  by  division,  and  in  this  manner  carry  on 
the  race  from  generation  to  generation ;  they  are  the 
instruments  of  heredity. 

All  growth  of  the  protoblasts  takes  place  by 
internal  processes — that  is,  by  intussusception. 

The  active  work  of  protoblasts  consists  in  :  («) 
formation  of  the  typical  organs  ;  (6)  special  move- 
ments of  the  protoplasDi — e.g.  amoeboid  movement ; 
(c)  the  formation  of  alloplasmatic  organs  (A.  Meyer). 
These  latter  are  derived  from  the  livmg  protoplasm, 
are  organised,  and  are  participating  themselves  in  the 
living  functions,  but  they  are  not  capable  of  multipli- 
cation by  division.  Such  alloplasmatic  organs  are  : 
cilia,  muscular  fibres,  nerve  cells  and  nerve  tibres,  and 
the  terminal  cells  in  the  sense  organs,  {d)  The  pro- 
duction of  passive,  partly  non-organised,  ergastic 
structures  (A.  Meyer),  or  formed  matter  (L.  Beale) ; 
such  are  the  cellulose  membranes  of  vegetable  cells, 
cuticular  formations,  fluids,  and  intercellular  and 
other  substances  (collagenous,  chondrinous,  osseous, 
elastic,  dental,  etc.),  cell-juices  and  granules  of  all 
kinds. 

Cells  ditfer  in  shape  according  to  kind,  locality, 
and  function,  being  spherical,  irregular,  polygonal, 
squamous,  branched,  spindle-shaped,  cylindrical,  pris- 
matic, or  conical.  These  various  shapes  will  be  more 
fully  described  when  dealing  in  detail  with  the  various 
kinds  of  cells.  Cells  in  man  and  mammals  differ  in 
size  within  considerable  limits  :  from  the  size  of  a 
small  white  blood  corpuscle  of  about  tt/ou  ^^  '"^"^  "^*^^^ 
to  that  of  a  laroe  ganglion  cell  in  the  anterior  horns  of 


Cells. 


the  spinal  cord  of  about  ^.^o  of  'ii^  inch,  or  to  that  of 
multinucleated  cells  of  the  bone  marrow — myeloplax — 
some  of  which  suri)ass  in  size  even  the  ganglion  cells. 
The  same  holds  good  of  the  nucleus.  Between  the 
nucleus  of  a  ganglion  cell  of  about  ^\-^  to  yaVo  ^^  ^^ 
inch  in  diameter  and  the  nucleus  of  a  white  blood 
corpuscle  of  about  -goVo  ^^  tit  wo  ^^  ^^^  inch  and  less 
there  are  all  intermediate  sizes. 

6.  Pi-otoplasiii  or  cytoplasm  is  a  transparent 
homogeneous  or  granular-looking  substance.  On  very 
careful  examin- 
ation with  good 
and  high  powers, 
and  especially 
^vhen  examined 
with  c  e  r  t  a  i  n 
reagents,  in 
many,  but  not 
in  all,  instances 
it  shows  a  more 
or  less  definite 
structure  (Fig. 
6),  composed  of 
fibrils,  more  or 
less  regular,  and 
in  some  instances  grouped  into  a  honeycomhed  re- 
ticulum, sjyongioplasm,  in  the  meshes  of  which  is 
a  homogeneous  substance,  /njaloplasm  (Leydig). 
The  closer  the  meshes  of  the  reticulum,  the  less 
there  is  of  this  interstitial  substance,  and  the 
more  regularly  granular  does  the  reticulum  appear. 
In  the  meshes  of  the  reticulum,  however,  may  be 
included  larger  or  smaller  granules  of  fat,  pigment, 
or  other  material.  Water  makes  protoplasm  swell 
up  and  ultimately  this  becomes  disintegrated  ;  so  also 
act  dilute  acids  and  alkalies.  All  substances  that 
coagulate  proteids  have  the  same  effect  on  protoplasm. 


Fig.  6. — Anictboid  pale  leucocyte  of  the  newt, 
showing  the  nuclei  embedded  in  the  cell  proto- 
Ijlasni— this  latter  consisting  of  spongioplasm 
and  hyaloplasm.     (After  Scho/er.) 


8 


Elements  of  Histology. 


In  arrangement  of  its  elements  the  spongioplasm 
ditfers  in  different  cells  ;  while  in  some — e.g.  spheroidal 
or  cubical  ej^ithelial  cells — it  is  as  a  rule  uniform  ;  in 
columnar  cells  it  is  elongated  in  the  direction  of  the 
long  axis  of  the  cell,  hence  the  reticulum  appears  as 
an  eminently  longitudinally  fibrillated  substance  ;  in 
ganglion  cells  it  is  concentrically  arranged.     In  some 


Fig.  7. — Cell  with  radially  disposed  reticulum  from  the  intestinal  epithelium 
of  a  worm.      (After  Carnoy,  from  Quain's  "Anatomy.") 

mc.  Cell  iiiembraiie  ;  j)c,  cell  protoplasm  ;   mn,  nuclear  membrane  ;   pn,  nuclear 
achromatin  surrounding  the  convoluted  chromatin  filaments  bn. 

cells  in  the  outer  portion  the  spongioplasm  possesses  a 
different  arrangement  from  that  in  the  middle  portion, 
and  then  a  division  is  made  between  ectoplasm  and 
endoplasni  (Fig.  7).  The  hyaloplasm  differs  in  amount 
in  different  cells,  and  in  the  same  kind  of  cells  it 
varies  according  to  different  states  of  cell  activity. 
Thus  in  gland  cells  during  activity  the  amount  of 
hyaloplasm  is  increased,  containing  in  these  instances 
more  or  less  of  jjranular  matter. 


Cells. 


In  amceboid  cells,  such  as  the  white  corpuscles  of 
the  blood,  the  hyaloplasm  is  the  substance  in  which 
the  spontaneous  or  amoeboid  changes  and  movement 
are  principally  lodged,  as  has  been  shown  by  instan- 
taneous electric  illumination  by  Strieker. 

In  the  protoplasm  of  many  cells  are  lodged 
granules  of  various  kinds,  microsomes  ;  they  differ  in 
size,  shape,  colour,  and  chemical  nature,  and  are,  as  a 
rule,  the  result  of  cell  activity.  Such  are  the  zymo- 
gen granules  in  secreting  gland  cells  ;  eosinophil e, 
basopliile,  and  neutrophile  or  amphophile  granules 
in  leucocytes  ;  glycogen  granules  in  the  liver  cells, 
cartilage  cells,  and  leucocytes  ;  pigment  granules  in 
various  kinds  of  jDigmented  cells ;  fat  granules  and 
fat  globules  in  wandering  cells,  in  connective-tissue 
cells,  in  liver  cells,  in 
the  epithelial  cells  of 
the  milk  gland,  etc.  It 
is  not  justifiable  to  as- 
sume with  Altmann  that 
these  microsomes  or  bio- 
blasts  are  living  entities 
in  the  sense  that  the 
whole  cell  is. 

In  the  cell  proto- 
plasm of  leucocytes,  of 
epithelial  and  other  cells, 
certain  granules  and 
fibrils  have  been  de- 
scribed by  Flemming, 
Boveri,  Heidenhain,  and 
others,  which  being  of 
a  constant  and   definite 

nature  play  an  important  part  in  the  division  of  the 
cell  and  its  nucleus.  This  is  the  centrosome,  and  with 
its  radiating  fibrillse  forms  the  attractionsjyJiere  (Fig.  8). 
The  centrosome  is  a  granule  surrounded  by  a  hyaline 


Fig.  8.— Leucocyte  of  Salamandra  con- 
taining two  nuclei,  and  showing  the 
attractionsphere  :  the  centrosome  is 
already  divided  into  two.  (After  Dr. 
Martin  Heidenhain.) 


ro 


Elements  of  IIistologv. 


spherical  space  ;  through  this  pass  the  fibrillse  radi- 
ating from  the  former,  aod  connect  it  with  the 
spongioplasm    of    the    cell    body.       The    whole — Le 


// '  '  -»— ^-^^-i '— — '^^ 


Fig.  9. — Blastomeres  of  Bi-segmented  0\-um  of  Ascaris   megalocephala 
{Ajter  Boveri,from  Kdllik'jr,  I.) 

A :  a,  Attractionsphere ;  v,  nucleus  in  resting-  state  ;  B :  nucleus  in  stage 
of  convolution:  c,  attractionsphere  nearly  divided;  D,  attract ionsphere 
divided:  E.  attractionspheres  arranged  at  the  poles,  chx-omosomes  forming 
tiiC  eauaiorial  plate. 


centrosome  and  radiating  tibrilhe — represents  the 
attractionsphere.  Preceding  the  division  of  the 
cell  nucleus,  the  centrosome  divides  into  two, 
each  daughter  centrosome,  with  its  own  hyaline 
areola  and  system  of  radiating  fibrillar,  forming 
by  -  and  -  by     a     separate     attractionsphere,     which 


Cells.  i  i 

migrating  towards  op})Ositc  pules  of  the  cell- 
Itody  become  separate  jjoints  of  attraction  for  the 
divided  nuclear  mitoma.  [See  division  of  nucleus.)  So 
that  the  division  of  the  attractionsphere  would  be 
the  tirst,  the  division  of  the  nucleus  the  second,  and 
the  division  of  the  cell  protoplasm  the  third  and  final 
stage  in  the  division  of  a  cell  (Fig.  9). 

7.  The  iiiicleiis,  the  size  of  which  is  generally  in 
proportion  to  that  of  the  cell,  is  usually  spherical  or 
oval.  It  is  composed  of  a  more  or  less  distinct  invest- 
ing cuticle  and  the  nuclear  contents  ;  the  former  is 
tlie  membrane,  the  latter  the  nuclear  substance,  karyo- 
plasm,  or  nucleoplasm.  This,  again,  is  composed,  in 
adult  nuclei,  of  a  stroma  or  network,  mitoma,  and  the 
inter-Jibrillar  suhsta^ice.  The  network  consists  of 
tibrils  of  various  thickness,  and  trabecular  or  septa 
more  or  less  irregular  in  thickness  and  length.  In- 
timately connected  with  and  lodged  in  the  network 
are  anijular  or  rounded  masses  called  nucleoli.  The 
number  and  size  of  these  vary  considerably  ;  in 
young  nuclei  they  may  be  large  and  numerous,  in 
adult  or  resting  nuclei  they  are  few,  and  in  those 
about  to  divide  they  are  altogether  absent.  Also  the 
network  is  subject  to  great  variation  :  while  in  adult 
or  resting  nuclei^  and  particularly  those  about  to 
divide,  the  network  is  of  great  uniformity  and  well 
developed  ;  it  may  be  very  imperfect  in  young  nuclei, 
in  which  it  is  sometimes  represented  by  a  number  of 
irregular  masses  joined  by  short  bridges.  The  more 
perfect  the  nuclear  network,  the  fewer  are  the  nucleoli. 
Owing  to  the  ready  manner  in  which  the  fibrils  of  the 
nuclear  network,  i.e.  the  mitoma,  take  up  certain  dyes, 
their  substance  is  called  chromatin,  and  the  fibrils 
are  the  chromosomes ;  while  the  inter-tibrillar  sub- 
stance not  possessed  of  this  character  is  called 
achromatin.  Occasionally,  also,  the  achromatin  ap- 
pears composed  of  fibrils,  and  these  are  then  called 


1 2  Elements  of  Histology. 

secondary  fibrils,  as  distinct  from  tlie  chromosomes  or 
})rimary  fibrils.  Rabl  and  with  him  Heidenhain 
maintain,  however,  that  the  achromatin  in  typical 
adult  nuclei  is  ahvays  composed  of  tine  fibrils,  and 
that  both  the  chromatin  and  achromatin  fibrils  possess 
a  definite  unipolar  arrangement  and  convergence, 
while  Carnoy  and  van  Gehuchten  assume  a  bipolar 
arrangement.  But  this  distinction  holds  good  only 
for  adult  nuclei ;  in  young  nuclei  the  whole  nuclear 
contents  may  possess  this  aflinity  for  the  same  dyes, 
and  in  this  case  the  whole  nucleus  becomes  uniformly 
stained.  The  nuclear  membrane  is  a  condensed  outer 
stratum  of  the  nuclear  network.  At  the  commence- 
ment of  the  division  of  the  nucleus  the  membrane 
disappears. 

In  some  instances  it  can  be  shown  that  the 
nuclear  filjrils  are  in  continuity  with  the  fibrils  of  the 
cell  substance.  In  the  moving  white  blood  corpuscles 
Strieker  and  linger  have  seen  the  nucleus  becoming 
one  with  the  cell  substance,  and  again  afterwards 
diti'erentiated  by  the  apjDearance  of  a  membrane. 

8.  During:  division  of  the  cell  the  nucleus 
generally  divides  before  the  cell  i)rotoplasm.  This 
division  of  the  nucleus  was  formerly  supj)osed  to 
occur  in  the  same  manner  as  that  of  the  cell  proto- 
plasm— i.e.  by  simple  cleavage.  This  mode  is  called 
the  direct  or  amitotic  division,  or  Remak's  mode  of 
division.  In  this  division  the  nucleus  is  supposed  to 
become  constricted,  kidney-shaped  and  hourglass- 
shaped  and,  if  the  division  is  into  more  than  two, 
lobed.  Nuclei  of  these  shapes  are  not  uncommon  ; 
but  they  need  not  necessarily  indicate  direct  division, 
because,  being  very  soft  structures,  pressure  exerted 
from  outside,  or  the  motion  of  the  cell  protoplasm, 
may  produce  these  shapes  ;  and,  further,  the  contrac- 
tility of  the  nucleus  may,  and  occasionally  has  been 
observed  to,  cause  these  changes  of  shape.      From  the 


Cells. 


^3 


ol>s('r\ations  of  Schneider,  Biitschli,  Folil,  Strass- 
burgor,  Mayzel,  van  Beiieden,  Schleicher,  Fleniiiiing, 
liabl,  and  others,  it  is  known  that  in  the  embryo  and 
adult,  in  vertebrates  and  invertebrates,  in  all  kinds  of 
cells,  both  in  the  noi'nial  as  well  as  morbid  condition,  the 
division  of  the  cell  protoplasm  is  preceded  by  complex 
changes  of  the  nuclear  mitoma,  leading  to  the  division 
of  the  nucleus  (Fig.    10).      The    sum-total    of    these 


Fig.  10. — Karyoinitosis. 
A,  Ordinary  nucleus  of  a  columiiar  opitlieli.al  cell :  b,  c,  the  same  nucleus  in  the 
stage  of  convolution  ;  D.  the  wreath,  or  rosette  form;  e,  the  aster,  or  single 
star;  F,  a  nuclear  spindle  from  the  Desceiin't's  endothelium  of  the  frog's 
Cornea;  G,  H,  I,  diaster  ;  k,  two  daughter  nuclei. 

changes  is  called  indirect  division,  karyokinesis 
(Schleicher)  or  karyomitosis  "^  (Flemming).  Where 
this  process  occurs  in  its  complete  and  typical  form, 
the  mitoma  passes  through  the  following  phases 
(Flemming,  Rabl)  : — 

i. — Convolution  or  spireme  or  shein  ;  disappearance 
of  the  nucleoli,  increase  of  the  fibrils  constituting  the 

*  Schleicher  noticed  that  the  fibrils  duriuo;  this  process  show 
movemeut ;  hence  the  name  Karyokinesis.     Mitosis  indicates  the 
r-    .  grouping  and  changes  of  the  fibrils  (MtTos  =  fibril). 


14  Elements  of  Histology. 

chromatic  substance,  at  the  same  time  the  fibrils 
become  free,  as  it  were,  and  bent  and  twisted  at  first 
into  a  dense,  afterwards  into  a  loose  convolution. 
The  fibrils  of  the  loose  convolution  are  thicker  than 
before,   less   twisted,  and  more  like  masses  of  loops. 


/ 


">  c 


t 


^  ^If 


^?\r'.4\:^ 


'^^^    ■-  .^^^'r>' 


^ 


(" 


Fig.  11. — Eiiithclium  of  iiiouth  of  einbiyo  salamander,  showing  nuclei  in 
various  stages  of  karyomitosis  (Flemming). 

These  latter  Ijy  cross  division  along  the  periphery  of 
the  mass  increase  in  number,  and  thereby  are  con- 
verted into  simple  loops,  arranged  more  or  less  like  a 
wreath  or  rosette.  The  whole  nucleus  is  larger  than 
before,  its  membrane  has  disappeared,  and  it  is  sur- 
rounded by  a  more  or  less  clear  halo  of  cell  proto- 
plasm (Fig.  11). 

ii. — Longitudinal  division  of  the  loops,  each  loop 
giving  origin  to  a  pair  of  sister  loops;  the  whole, 
viewed  from  the  surface,  looks  like  a  star  of  numerous 
fine  fibrils,  joined  centrally  so  as  to  form  single  loops. 


Cells. 


15 


iii. — The  nuclear  sjnndle^  a  spindle  shaped  ar- 
rangement of  tine  threads  of  (possibly)  achromatin 
extending  between  two  opposite  points  of  the  cell 
protoplasm  ;  these  points  are  the  poles,  and  the 
transverse   line    midway   between    them — i.e.   at  the 


c 

Fig.  12. — Karyomitosis.     {Ajter  KolUker.) 

A,  Spireme  ;  b,  diasier;   c,  ilie  nucleus  lias  divuled,  cUe  prucoi'lasiu  of  the  cell 
In  tbe  act.  of  dividing. 

broadest  part  of  the  spindle — is  called  the  equator. 
At  each  pole  the  threads  of  the  spindle  are  connected 
with  a  granule  of  the  cell  protoplasm,  tlie  pole  cor- 
puscle or  centrosome,  mentioned  on  a  previous  pa^-e ; 
from  the  centrosome  radiate  numerous  fine  fibrillar, 
connecting  the  centrosome  or  pole  corpuscle  with  the 
cell  protoplasm,  thus  forming  "  the  suns  "  or  attraction- 
spheres,  one  at  each  pole  (van  Beneden). 

The  above-named  sister  loops  so  arrange  themselves 
about  the  equator  of  the  spindle  as  to  form  a  star — 
the  motJier-star,  monaster,  or  aster.  In  this  arrange- 
ment the  vertex  of  the  loops  is  directed  inwards,  the 
open  limbs  outwards.  Seen  in  profile  the  aster  would 
appear  like  a  narrow  granular  -  looking  plate  of 
chromosomes — the  nuclear  plate. 

iv. — Metakinesis  :  Of  each  pair  of  sister  loops  form- 
ing the  aster   one  loop  is   attracted  by — i.e.  migrates 


1 6  Elements  of  Histology. 

towards  one,  tLe  otlier  towards  the  other  pole  of  the 
spindle:  that  is,  towards  the  attractionspheres,  the 
vertex  of  the  loops  always  leading. 

V. — Diaster  :  arrived  at  tlie  pole,  the  loops  form 
again  an  aster  or  daughter  star  for  each  pole  (Fig.  12). 

\i. — Dispireme  :  the  threads  of  each  star  become 
convoluted. 

ZS^ow  follows  usually  the  division  of  the  cell  proto- 
plasm in  the  line  of  the  equator  of  the  spindle. 

vii. — In  the  last  phase  all  traces  of  the  spindle  are 
lost :  a  membrane  appears  around  each  of  the  two 
new  nuclei,  and  the  threads  of  the  dispireme  become 
branched  and  connected  into  a  network. 

From  the  forecjoin^;  it  is  clear  that  during  division 
an  intimate  fusion  Vjetween  cell  protoplasm  and 
nucleus  takes  place  :  («)  by  the  fusion  of  the  nuclear 
interstitial  suVjstance  with  the  cell  protoplasm  after 
the  disappearance  of  the  nuclear  membrane  ;  and  (h) 
bv  the  connection  of  the  nuclear  spindle  with  the 
centrosomes  and  attractionspheres,  the  fibrils  of  the 
latter  being  part  of  the  cell  protoplasm. 

It  ought  to  be  mentioned,  however,  that  some 
histolo^ists  do  not  rec;ard  the  fibrils  of  the  nuclear 
Spindle  as  part  of  and  derived  from  the  original 
nuclear  substance  (achromatin).  Boveri  regards  the 
fibrils  of  the  spindle  as  derived  from  the  cell  proto- 
plasm and  as  forming  part  of  the  attractionspheres 
— i.e.  those  fiVjrils  which  remain  connecting  the  two 
attractionspheres,  and  which  finally,  after  the  nuclear 
division  has  Ijeen  completed,  by  their  transverse 
division,  mark  off  and  initiate  the  final  stage — that  is, 
the  division  of  the  cell  body. 

While  these  various  details  and  phases  in  the 
changes  and  division  of  the  centrosome  and  attrac- 
tionsphere  are  well  enough  marked  in  the  ovum,  as  is 
also  their  relation  to  the  chromosomes  of  the  dividing 
ovum  nucleus,  it  is  not  sufficiently  established  that 


Cells.  i  7 

the  above  are  of  general  occurrence  in  the  division  of 
adult  cells;  the  attractionsphere  and  its  division  have 
])een  observed  only  in  a  few  such  instances — e.g.  in 
the  leucocytes  of  salamander  and  man. 

In  some  cases  the  process  of  karyomitosis  has  Vjeen 
found  to  be  atypical,  inasmuch  as  some  of  the  above 
phases  are  left  out,  as  it  were  ;  while  in  other  cases 
the  nuclear  division  takes  place  already  during  the 
earlier  phases — e.g.  in  the  phase  of  the  spireme. 
When  the  nucleus  divides  into  two  or  three  or  more 
nuclei  without  the  cell  protoplasm  also  undergoing 
division,  a  cell  with  two,  three,  or  more  nuclei  is  the 
result. 

Multiplication  of  the  nucleus  by  budding  and 
direct  fission  has  also  been  observed,  but  it  is  quite 
possible  that  this  process  is  only  as  a  sort  of  imper- 
fect and  abnormal  karyomitosis. 

This  mode  [)robably  jDlays  a  more  important  part 
than  the  typical  karyomitosis,  whenever  rapid  multi- 
plication and  rei^roduction  are  necessary.  Thus,  for 
instance,  while  in  the  epithelium  cells  covering  the 
anterior  surface  of  the  normal  cornea  of  the  newt  and 
frog  here  and  there  a  nucleus  can  Ije  seen  which 
shows  the  process  of  typical  karyomitosis,  such  forms 
cannot  be  found  in  cases  of  rapid  regeneration  of 
that  epithelium.  For  example,  after  removing  the 
whole  thickness  of  the  anterior  epithelium  from  the 
middle  part  of  the  cornea,  rapid  multiplication  of  the 
epithelium  cells  takes  place,  starting  from  those 
immediately  around  the  defect ;  in  consequence  of 
this,  in  two  or  three  days  the  defect  becomes  again 
quite  covered  with  the  new  epithelium.  Xow,  ex- 
amining the  epithelium  cells  at  the  margin  of  the 
defect,  as  well  as  those  gradually  pushed  over  and 
covering  the  defect,  none  of  the  nuclei  are  found  in 
any  of  the  phases  of  typical  karyomitosis  ;  while  a 
few  days  later,  after  the  defect  is  covered  by  the  new 
c 


1 8  Elements  of  Histology. 

epithelium,  there  is  no  difficulty  in  finding  nuclei  in 
one  or  another  ])lia.se  of  the  typical  kar3"omito.sis. 

Paranuclei   and  cell   enclosures, — It    was 

mentioned  above  that  cells  may  and  do  include  in 
their  j^rotoplasm  formed  substances  like  granules 
of  various  kinds,  fat  globules,  pigment,  etc.  ;  but  in 
addition  to  these,  and  distinct  from  the  attraction- 
spheres  mentioned  on  a  former  page,  occasionally  the 
cell  substance  includes  corpuscles  of  an  altogether 
different  nature.  These  corpuscles,  in  size  and  staining 
power,  resemble  the  cell  nucleus  or  parts  thereof,  and 
as  a  matter  of  fact  are  derived  from  the  cell  nucleus. 
Balbiani  has  called  such  bodies  in  the  ovum  cell 
'paranuclei^  and  Griitzner  has  applied  the  same  term 
to  those  that  occur  in  the  gland  cells  of  the  pancreas. 
Now  it  is  a  fact  that  preceding  the  segmentation 
of  the  ovum,  and  preceding  the  fusion  of  the  sperm- 
and  ovum-pronucleus,  part  of  this  latter  is  eliminated, 
and  the  same  occasionally  is  observed  to  take  place 
in  other  cells  prior  to  the  division  of  the  nucleus, 
as  also  under  various  pathological  conditions.  The 
eliminated  body  or  bodies,  known  as  polar  bodies, 
are  part  of  the  original  nuclear  substance,  principally 
the  chromatin.  The  paranucleus  is  as  a  rule  smaller 
than  the  cell  nucleus,  lies  close  to  this,  and  has 
similar  affinit}''  to  the  dyes  which  stain  the  nucleus 
itself. 


19 


CHAPTER    IT. 

BLOOD. 

9.  Under  the  microscope  blood  appears  as  a 
transparent  Huid,  the  liquor  sanguinis  or  plasina,  in 
which  float  vast  numl^ers  of  formed  bodies,  the  blood 
corpuscles.  The  great  majority  of  these  are  coloured ; 
a  few  of  them  are  colourless.  The  latter  are  called 
ivhite  or  colourless  blood  corpuscles,  or  leucocytes  ;  the 
former  are  called  red  or  coloured  blood  coryuscles,  or 
blood-discs.  They  appear  red  only  when  seen  in  a 
thick  layer ;  when  in  a  single  layer  they  appear  of 
a  yellow-greenish  colour,  more  yellow  if  of  arterial, 
more  green  if  of  venous,  blood.  The  proportions  of 
plasma  and  blood  corpuscles  are  sixty-four  of  the 
former  and  thirty-six  of  the  latter  in  one  hundred 
volumes  of  blood.  By  measurement  it  has  been  found 
that  there  are  a  little  over  five  millions  of  blood  cor- 
puscles in  each  cubic  millimetre  {y-^^o^y  of  ^  cubic 
inch)  of  human  blood.  There  appears  to  be  in  healthy 
human  blood,  on  an  average,  one  white  corpuscle  for 
600-1200  red  ones.  In  man  and  mammals  the  re- 
lative number  of  blood  corpuscles  is  greater  than 
in  birds,  and  in  birds  greater  than  in  lower  verte- 
brates. 

The  number  of  red,  and  also  of  white,  corpuscles 
is  subject  to  variation,  both  in  health  and  disease. 
After  profuse  haemorrhage,  the  number  of  red  cor- 
puscles is  temporarily  greatly  reduced,  but  in  a  short 
time,  it  may  be  even  in  twenty-four  to  forty-eight 
hours,  they  may  approach  again  the  normal  number ; 


2o  Elemexts  of  Histology. 

in  constitutional  chronic  diseases  the  number  of  red 
corpuscles  is,  as  a  rale,  decreased ;  so  also  in  anj^mia, 
spontaneous  or  following  acute  infectious  diseases, 
fevers,  etc.  The  number  of  white  corpuscles  is  always 
greater  after  a  copious  meal  than  during  fasting. 
Certain  diseases  are  associated  with  a  decrease,  others 
wi.th  an  increase,  of  the  white  corpuscles  of  the  cir- 
culating blood ;  the  decrease  when  pronounced  is 
spoken  of  as  leucopenia^  the  increase  as  leucocy- 
th(emia^  leucctmia,  or  leucocytosis. 

10.  The  red  blood  corpuscles  (Fig.  13)  of  man 
and  mammals  are  homogeneous  bi-concave  discs  (ex- 
cept in  the  camelida?,  where  they  are  elliptical),  and 
do  not  possess  any  surroundmg  membrane  or  nucleus. 
Being  bi-concave  in  shape,  they  are  thinner  and 
more  transparent  in  the  centre  than  at  the  periphery. 
In  other    vertebrates    they    are    oval,  and    more    or 

less  flattened  from 
side  to  side,  and  each 
possesses  a  central 
oval  nucleus. 

The     diameter     of 

Fig.  13. — ^arious  kiuds  of  Red  Blood  i        ,  i    i  i        i 

Corpuscles.  the  human    red   blood 

A,  Two  human,  one  seen  flat,  the  other  COrpUScle         is  about 

edgeways ;    b,  a  red  corpuscle  of  the  ■■  p  "       1        ' 

camel;   c,  two  red  corpuscles  of  the  solTo  '^^^      mCll      111 

frog,   one   seen  from  the   liroad,    the  \  ■\,\  ■  i  , 

other  from  the  narrow  side.  DreaCltn,  I.e.        aOOUt 

7  "8  ^.  and  its  thick- 
ness about  ^  ^QQQ  of  an  inch.  But  there  are  always 
corpuscles  present  which  are  much  smaller  by  about 
one-third  to  one-half  than  the  others — microcytes.  In 
normal  blood  these  microcytes  are  scarce  :  but  in 
certain  abnormal  conditions,  especially  in  pernicious 
anfemia,  they  are  conspicuous  by  their  number. 

According  to  Gulliver,  ^A'elcker,  and  others,  tlie 
followinof  are  the  averagfe  diameters  of  the  red  blood 
corpuscles  of  various  vertebrates  :    Man,  -3-2V0  J  ^^i 


08 


A 


"3 'sou  '     ^"^j     4cFo^  y     outc|7,     5 0 00^  }     v.iv>^jii«.ij.v,     :jTi  5"  ^ 


1      •     cat,    ^ J^ ;    sheep,    ^^W  i    elephant, 


Blood. 


21 


horse,  j:^ 
1 


\ . 

6  ()  O   ' 

10  4  3  ;  "ewt, 
1 

1  1  -t  2  • 
11 


musk  deer,  y^i^  5  ;  pigeon,  ^g^y  ;  toad, 
proteus,  yl^ ;   pike,  ^-qVo  ;  ^li^^i'k, 


1^ 

S  1  i 


In  a  microscopic  specimen  of  fresh  unaltered 
blood  (Fig.  14)  the  red  blood  corpuscles  form  peculiar 
short  or  long  rolls,   like 
so  many  coins,  from  be- 
coming adherent  to  one 
another    by  their    broad 
surfaces.     Under  various 
conditions   —  such       as 
Avhen  isolated,    or   when 
blood   is    diluted   with  a 
7*5-l  p.c.  saUne  solution 
or  solutions  of  other  salts 
(sulphate    of    sodium    or 
magnesium)  —  the    cor- 
puscles lose  their  smooth     ^• 
circular   outline,   shrink- 
ing and  becoming  crenate 
(Fig.    15,  a).     In  a  further 
lose    their    discoid    form,    and    become 
spherical,   but  beset  all  over  their  sur- 
face with  minute  processes.     This  shape 
is  called  the  liorse-chestnut  shaj^e  (Fig.  15, 
b,   c).     It  is  probably  due   to  the   cor- 
puscles   losing    carbonic    acid,    as    the 
addition  of  the  acid  brings  back  their 
discoid  shape  and  smooth  circular  out- 
line.    On  abstracting  the  carbonic  acid 
they  return  to  the  horse-chestnut  shaj)e.    , 
Water,  acid,  alcohol,  ether,  the  electric 
current,     and     many     other    reagents, 
produce    decoloration    of    the    red    blood 


Fig.  14. — Human  Blood,  fresh. 

Piouleaux  of  red  corpuscles ;  b,  iso- 
lated red  fdrpuscle  seen  in  pr<5flle  ;  c, 
isolated  red  corpuscle  seen  flat ;  D, 
•ttliite  corpuscles. 


stage 


of  shrinking 
smaller 


they 
and 


a 

o  o 


Fi 


h  ^' 

15. — Human 
Red  Blood 
Corpuscles. 

Crenate;  b,  c, 
horse-cbestnut- 
sliaped. 

corpuscles. 


the  coloured  matter — generally  the  combination  of 
the  blood-colouring  matter  with  globulin,  known 
as    hcenioylohin — becoming    dissolved   in  the  plasma. 


2  2  Elements  of  Histology. 

What  is  left  of  the  corpuscles  is  called  the 
stroma.  In  ne^^i;'s  and  frog's  blood  a  separation 
of  the  stroma  from  the  nucleus  and  haemoglobin  can 

be  effected  by  means  of 
^    ^  a'^  ^c^  boracic  acid(Fig.  16,  b); 

"  Ai.      ^i       \^'  ^8  ^F\  c     ^^^^    former   is  called  by 


O  ^  {€^)       Briicke    the    oekoid,    the 


U^       B 


latter  zooid.  This  stroma 
contains    amongst    other 

Fig.    IG.— Red    Blood    Corpuscles    of    things     mucll    paraf'lobu- 
Man  and  Xewt.  t  mi  j.  c  J.^ 

,     ^     ^,        .       im.      I  he   stroma  or  the 

A,  Human  red  corpuscles  after  the  action  ,  i   -i   • 

of  tannic  acid;  a,  tbree  red  corpuscles,     COrDUSCles  Ot  amplllljiaUS 
from  which  the  hierauf^loliin  is  pass-     .       ■•■  •'• 

ing  out:  5. Roberts's  corpuscles.    B,    is    scen,     undcr    Certain 

^ewt  s  red  corpusdesafter  theaction  ' 

of  boracic  acid;  a,  corpuscle. show-    reao^ents,   to  be  of  a  re- 

mg  Briicke  s   zooid   and   cekoid  ;&,."' 

corpuscle    showing    the    reticulated     tlCUlated     StrUCture,     but 

stroma ;    c,    corpuscle    showins   the      •  ^        c         i 

reticulum  in  the  nucleus;  d,  thenu-     ]n  the  fresh  state  appears 

cleus  passing  out.  ^^ 

homogeneous  and  pale. 
Decoloration  of  the  blood  corpuscles  can  also  be 
observed  to  take  place  in  blood  spontaneously  without 
the  addition  of  any  reagents  or  with  that  of  indifferent 
fluids,  such  as  the  aqueous  humour  of  the  eye,  hydro- 
cele fluid,  etc.  The  number  of  corpuscles  undergoing 
decoloration  under  these  conditions  is,  however,  small, 

When  blood  is  dried  on  a  glass  in  a  thin  tilm, 
the  corpuscles,  forming  a  single  layer  onh",  dr}^  on 
before  they  shrink,  and  thus  retain  their  natural  size 
and  outline  ;  their  strouia  can  then  be  easily  stained 
with  aniline  dyes. 

12.  The  haeiiioglotoiii  of  the  red  blood  cor- 
puscles forms  crystals  (Fig.  17),  which  differ  in  shape 
in  various  mammals.  They  are  always  of  microscopic 
size,  and  of  a  bright  red  colour.  In  man  and  most 
mammals  they  are  of  the  shape  of  prismatic  needles 
or  rhombic  plates ;  in  the  squirrel  they  are  hexagonal 
plates,  and  in  the  guinea-pig  they  are  tetrahedral  or 
octahedral. 

The  blood  pigment  itself  is  an  amorphous  dark- 


Blood. 


23 


brown  or  l)l;ick  powder — the  luematin  ;  but  it  can  be 
obtained  in  a  crystalline  form,  as  liydrochlorate  of 
hi\iinatin  (Fig.  18).  These  crystals  also  are  of  micro- 
scopic size,  of  a 
nut-brown  colour, 
of  the  shape  of 
nari'ow  rhombic 
plates,  and  are 
called  lut^rnin  cry- 
stals, or  Teich- 
mann^s  crystals.  In 
extravasated  hu- 
man blood,  crystals 
of  a  bright  yellow 
or  orange  colour 
are  occasionally 
met  with  ;  they  are 
coverer,  hctmatoidin. 
tical  with  bilirubin 
human  bile. 

13.  The  white  or  colourless  cor- 
puscles, or  leucocytes,  are  in  human 

blood  of  about  2-5  00  ^^  2"5Vo  *^^  ^^  ^^^^ 
in  diameter — i  e.  about  10  fi — and  are 
spherical  in  the  circulating  blood  or  in 
blood  that  has  just  been  removed  from  the  vessels.  Their 
substance  is  transparent  granular-looking  protoplasm, 
some  containing  larger  or  smaller  distinct  granules. 
These  granules  are  not  all  of  the  same  nature,  as 
will  presently  appear.  In  some  kinds  of  blood,  notably 
horse's,  they  are  of  a  reddish  colour,  and  these 
corpuscles  were  supposed  by  some  observers  (Semmer 
and  Alexander  Schmidt)  to  be  intermediate  between 
red  and  white  corpuscles.  The  protoplasm  of  the 
colourless  corpuscles  contains  occasionally  glycogen 
(Ranvier,  Schiifer).  In  the  blood  of  the  lower  verte- 
brates the  colourless  corpuscles  are  much  larger  than 


Fig.  17. — Hitmoglobin  crystals. 
A,  Of  guinea-pig ;  b,  of  siiuirrel ;  c,  D,  buiuan. 

called    by   Yirchow,    their   dis- 
They  are  supposed  to  be   iden- 
obtainable     from 


Fig.  IS.— Ha-miii 
crystals. 


24 


Elements  of  Histology. 


in  mammals.  But  in  all  cases  tliey  consist  of  proto- 
plasm (spongioplasm  and  hyaloplasm),  include  one, 
two,  or  more  nuclei,  and  show  amoeboid  movement. 
This  may  he  observed  in  corpuscles  without  any 
addition  to  a  fresh  microscopic  specimen  of  blood, 
but  it  always    becomes    much    more    jironounced    on 


Fig.  19. —Phagocyte  (with  three  nuclei)  from  the  iieritoneal  fluid  of  a 
guinea-pig,  iireviously  injected  intraperitoneally  with  cholera  culture. 
The  interior  of  the  phagocyte  contains  numerous  degenerated  comma 
bacilli.     (Photo,  highly  magnified.) 


applying  artificial  heat  of  about  the  degree  of 
mammals'  blood.  It  is  then  seen  that  either  they 
throw  out  longer  or  shorter  filamentous  processes, 
which  may  gradually  lengthen  or  be  withdrawn, 
or  the  corpuscle  changes  its  position  either  by  a 
flowing  movement,  or  it  pushes  out  a  filamentous  pro- 
cess and  shifts  its  body  into  it.  During  this  move- 
ment the  corpuscle  may  take  up  granules  from  the 


Blood.  25 

siuToiinding  lluicl.  Leucocytes,  be  they  in  the  blood 
or  in  connective  tissue  or  lymph  glands  {see  below), 
that  can,  and  in  certain  circumstances  do,  take  up 
granules  or  similar  matter  are  spoken  of  as  phagocytes 
(eating    cells)    (Figs.    19,    20).      Division    by   simple 


^ 


Fig.  20. — Hyaline  Leucocytes  (pus  cells)  from  purulent  matter  ;  the  leuco- 
cytes contain  in  their  hyaline  protoplasm  two,  three,  or  more  nuclei 
two  of  the  cells  contain  in  their  protoplasm  a  number  of  cocci,  these 
cells  acting  as  phagocytes.     {Photo,  highly  magnified.) 


cleavage  of  leucocytes  of  the  blood  of  lower  verte- 
brates has  been  directly  observed  by  Klein  and 
Ranvier. 

14.  The  white  corpuscles  or  leucocytes  in  the 
same  sample  of  blood  differ  in  size  and  aspect.  They 
may  be  classed  into  three  groups  :  (a)  The  li/m2)hocyte, 


2  6  Elements  of  Histology. 

a  small  cell  possessed  of  a  relatively  large  single  nucleus 
surrounded  by  a  narrow  zone  of  protoj^lasm.  (6)  The 
typical  leucocyte  or  liyaline  leucocyte  is  larger  than  the 
former,  contains  two,  three,  or  even  four  relatively 
small  nuclei ;  its  cell  protoplasm  appears  hyaline, 
but  includes    a    spongy   network.     This    leucocyte  is 


Fig.  "21. — Frog's  Blood,  showing  red  blood  discs  and  one  oxypliile  white 
cell.     (Photo,  highly  magnified.) 

as  regards  numbers  by  far  the  predominating  white 
corpuscle,  and  its  amceboid  movement  is  very  striking, 
(c)  The  gramdar  leucocyte  forms  a  small  minority,  it 
contains  a  single  large  nucleus,  occasionally  two,  and 
its  cell  })rotoplasm  contains  conspicuous  granules. 

The   lymphocytes   are   identical  with  similar  cor- 
puscles of  the   adenoid  tissue  of  lymph  glands,  from 


Blood.  27 

Nvliicli  ill  all  probability  they  are  derived.  It  is  highly 
probable  that  they  are  young  forms  of  the  typical 
leucocytes.  The  grnnidar  leucocytes — i.e.  the  white 
corpuscles  that  contain  real  gi'anules — behave  dif- 
ferently when  subjected  to  staining  with  aniline  dyes. 
In  some  the  granules  stain  readily  with  acid  aniline 
dyes — e.g.  eosin — so  that  they  become  bright  red — 
eosinophile  (Ehrlich)  or  o.vi/phile  cells  (Fig.  21);  in 
others  the  granules  stain  only  in  basic  aniline  dyes 
— hasopJi  He  cells  ;  in  still  others  they  stain  both  with 
acid  and  alkaline  aniline  dyes — neutrophile  or  amjjho- 
phile.  "What  the  exact  relation  of  these  different 
granule-cells  amongst  themselves  and  to  the  non- 
granular or  hyaline  cells  is,  is  not  definitely  established. 
But  it  appears  from  the  researches  of  Kanthack  and 
Hardy  that  in  the  frog,  at  any  rate,  and  probably  also 
in  the  mammal,  the  oxyphile  or  eosinophile  leucocyte 
does  not  act  as  a  phagocyte,  and  that  this  function  is  mo- 
nopolised by  the  other  or  hyaline  variety  of  leucocytes. 
15.  In  every  microscopic  specimen  of  the  blood 
of  man  and  mammals  are  found  a  variable  number 
of  large  granules,  more  or  less  angular, 
singly  or  in  groups.  According  to  f^ 
Max   Schultze  they  are  derivatives  of  e^\ 

broken-up    white    corpuscles  ;    but    ac-        ^S  ^^ 
cording  to  Bizzozero,  they  are  present  ^ 

al read}' in  the  living  and  fresh   blood,  ©    o^ 

as     pale,     circular,    or     sliijhtly     oval    „.    ,.,    „ 

T-i-         ->-»      7\         rr<i      •         •         •  FiLT.  22.— Human 

discs  (Fig.   22,   0).     Their  size  is  only       ^   Biooti. 
1  to  i   of  that  of  the   red   blood  cor-    «.  R^d  bino.i  cor- 
puscles.     They  are  called  bv  him  bhod      platelets  of  biz- 

■•■  •'  "^  zdzero. 

platelets^  and  he  supposes  them  to  be  of 
essential  importance  in  the  coagulation  of  the  blood, 
originating  the  tibrin  ferment.  Hayem  described  them 
previously  as  being  intermediate  forms  in  the  de- 
velopment of  red  blood  corpuscles,  and  called  them 
hjematoplasts, 


2  8  Elements  of  Histology. 

16.   Development   of  blood    eorpiii^cles. — 

At  an  early  stage  of  embryonic  Jife,  when  blood  makes 
its  appearance  it  is  a  colourless  fluid,  containing  only 
white  corpuscles  (each  with  a  nucleus),  which  are  de- 
rived from  certain  cells  of  the  mesoblast.  These  white 
corpuscles  change  into  red  ones ;  the  protoplasm 
becomes  homogeneous  and  yellow  ;  then  it  assumes  a 
flattened  shape,  and  is  in  reality  a  coloured  blood 
corpuscle  containing  a  pale  nucleus.  All  through 
embryonic  life  new  white  corpuscles  are  transformed 
into  red  ones.  In  the  embryo  of  man  and  mammals 
these  red  corpuscles  contain  their  nuclei  for  some 
time,  but  ultimately  lose  them.  Xew  red  blood  cor- 
puscles may,  however,  be  formed  also  by  division  of 
nucleated  red  corpuscles.  Such  dis'ision  has  been 
observed  even  in  adult  blood  of  lower  vertebrates 
(Peremeschko)  as  well  as  in  the  foetus  of  mammals. 

The  cells  of  the  mesoblast  which  cHve  origin  to 
vessels  (cysts  and  strands)  are  capable  of  producing 
by  budding  and  cleavage  new  white  cells,  which  ulti- 
mately change  into  red  corpuscles.  (*See  formation  of 
blood-vessels.) 

An  important  source  for  the  new  formation  of  red 
corpuscles  in  the  embryo  and  adult  is  the  red  marrow 
of  bones  (Neumann,  Bizzozero,  E-indfleisch),  in  whicli 
numerous  nucleated  protoplasmic  cells  (marrow  cells) 
are  converted  into  nucleated  red  blood  corpuscles — 
erythrohlasts.  The  protoplasm  of  the  corpuscle 
becomes  homogeneous  and  tinged  with  yellow,  the 
nucleus  being  ultimately  lost.  The  spleen  is  also 
assumed  to  be  a  place  for  the  formation  of  red  blood 
corpuscles.  Again,  it  is  assumed  that  ordinary  white 
blood  corpuscles  are  transformed  into  red  ones,  but  of 
this  there  is  no  conclusive  evidence.  In  all  these 
instances  the  protoplasm  becomes  homogeneous  and 
filled  with  liEemoglobin,  while  the  cell  grows  flattened, 
discoid,  and  the  nucleus  in  the  end  disappears. 


Blood.  29 

Schiifer  described  intracellular  (endogenous)  for- 
mation of  red  blood  corpuscles  at  first  as  small  liH;mo- 
i;lobin  particles,  but  soon  growing  into  red  blood  cor- 
puscles in  certain  cells  of  the  subcutaneous  tissue  of 
young  animals.  Malassez  describes  the  red  blood  cor- 
puscles originating  by  a  process  of  continued  budding 
f I'om  the  marrow  cells. 

The  white  corpuscles  appear  to  be  derived  from 
the  lymphatic  organs,  whence  they  are  carried  by  the 
lymph  into  the  circulating  blood. 


CHAPTER     III. 

EPITHELIUM. 

17.  Epitlielial  cells  (Fig.  23)are  nuchated proto- 

2)Io.srnic  cells  for ming  co/dinuoas  masses  on  the  surface 
of  the  skin,  of  the  lining  membrane  of  the  alimentary 
canal,  the  respiratory  organs,  the  urinary  and  genital 
organs,  the  free  sui'face  of  the  conjunctiva,  and  the 
anterior  surface  of  the  cornea.  The  lining  of  the 
tubes  and  alveoli  of  secretin^  and  excretinoj  slands, 
such  as  the  kidney,  liver,  mammary  gland,  testis  and 
ovary,  the  salivary  glands,  mucous,  peptic,  and 
Lieberkiihn's  glands,  the  sweat  and  sebaceous  glands, 
the  hair  follicles,  etc.,  consists  of  epithelial  cells. 
Such  is  the  case  also  with  the  sensory  or  terminal 
parts  of  the  organs  of  the  special  senses.  And, 
finally,  epithelial  cells  occur  in  other  organs,  such  as 
the  thyroid,  the  pituitary  body,  etc. 

The  bail's  and  nails,  the  cuticle  of  the  skin, 
certain  parts  of  the  rods  and  cones  of  the  retina,  and 
the  rods  of  Corti  in  the  organ  of  hearing,  are  modified 
epithelial  structures. 

Epithelial  cells  are  grouped  together  by  ex- 
ceedingly thin  layers  of  an  albuminous  interstitial 
cement  substance,  which  duiing  life  is  of  a  semi- 
fluid nature,  and  belongs  to  the  gi'oup  of  bodies 
known  as  globulins. 

18.  As  rec:ards  shape,  we  distinguish  two  kinds 
of  epithelial  cells — columnar  and  squamous.  The 
columnar  cells  are  short  or  long,  cylindrical  or  pris- 
matic, pyramidal,   conical,    club-shaped,   pear-shaped, 


Epithelium. 


31 


or  spindle-shaped  ;  their  nucleus  is  always  more  or 
less  oval,  their  protoplasm  more  or  less  longitudinally^ 
striated,  l)eing  a  spongy  reticulum  with  predominantly 


longitudinal  arrange- 
ment. On  the  free 
surface  of  the  cells 
— i.e.  the  part  facing 
or 
-in 
a 
or 


r 


f^=f~ 


a  cavity,    canal, 
general    surface - 
many     instances 
Ijright    thinner 
thicker        cuticular 
structure     is     seen, 
with    more    or    less 
distinct  vertical  stri- 
ation.     The   conical 
or    spindle  -  shaped, 
club  -  shaped,      and 
pear-shaped  cells  are 
drawn     out     into 
longer     or     shorter 
single    or    branched 
extremities. 

The   squamous    or 
polyhedral    or  scalj 


Fig.  23.— Various  kinds  of  Epithelial  Cells. 

A,  Columnar  cells  of  intestine;  b.  polyhedral 
cells  of  the  conjunctiva;  c,  ciliated  conical 
cells  of  the  trachea ;  d,  ciliated  cell  of 
frog's  mouth ;  E.  inverted  conical  cell  of 
trachea;  f,  squainous  cell  of  the  cavity  of 
inouth,  seen  from  its  broad  surface ;  G, 
squamous  cell,  seen  edgeways. 


pavement  cells  are  cubical. 
The  nucleus  of  the  former  is 
almost  spherical,  that  of  the  latter  flattened  in  pro- 
portion to  the  thinness  of  the  scales.  In  polyhedral 
cells  it  can  be  shown  that  the  uniform  granulation  is 
due  to  the  regular  honeycombed  nature  of  the  cell 
protoplasm. 

19.  As  regards  size,  the  epithelial  cells  dilfer 
considerably  from  one  another  in  different  parts,  and 
even  in  the  same  part.  Thus,  the  columnar  cells, 
covering  the  surface  of  the  ^^Ili  of  the  small  intestine, 
are  consideraljly  longer  than  tho.se  lining  the  mucous 
membrane  of  the  uterus  :  the  columnar  cells  lining 
the  larger  ducts  of  the  kidney  are  considerably  longer 


z^ 


Elements  of  Histology. 


-  Three    Mucus-secreting 
Goblet  Cells. 

A,  From  the  jitomach  of  newt ;  B,  from 
a  mucous  glaml;  c,  from  tbe  sur- 
face of  the  mucous  membrane  of 
the  intestine. 


regards    ar- 


than  tliose  lining  the  small  ducts  ;  the  polyhedral 
cells  covering  the  anterior  surface  of  the  cornea  are 
considerably  smaller  than  those  on  the  surface  of  the 
lining  membrane  of  the  urinary  bladder ;  the  scales 
lining  the  ultimate  recesses  of  the  bronchial  tubes — 

the  air  cells  —  are  con- 
siderably smaller  than 
those  on  the  surface  of 
the  membrane  lining  the 
human  oral  cavity  and 
oesophagus  (Fig,  24). 

20.  As 
raiig:eiiieiit,  the  epithe- 
lial cells  are  arranged 
as  a  sinfjle  layer  or  are 
stratified,  forming  several 
superposed  layers  ;  in  the 
former  case  we  have  a  sin^le-lavered,  in  the  latter  a 
stratified  epithelium.  The  simple  epithelium  may  be 
composed  of  squamous  cells,  simjyle  squamous  or  simple 
jjavement  epitJiellum  ;  or  it  may  be  composed  of  columnar 
cells,  siinple  coliLinnar  epithelium.  The  stratified  epithe- 
lium may  be  stratified  pavement  or  stratified  columnar  ; 
in  the  former  case  all  or  the  majority  of  the  layers 
consist  of  squamous  or  polyhedral  cells;  in  the  latter 
all  cells  belong  to  the  columnar  kind.  Simple 
squamous  epithelium  is  that  whicli  lines  the  air  cells, 
certain  urinary  tubules  of  the  kidney  (the  looped 
tubes  of  Henle,  the  cortical  parts  of  the  collecting 
tubes),  the  acini  of  the  milk-gland,  the  inner  surface 
of  the  iris  and  choroid  membrane  of  the  eyeball. 
Simple  columnar  epithelium  is  that  on  the  inner 
surface  of  the  stomach,  small  and  large  intestine, 
uterus,  small  bronchi,  ducts  and  acini  of  mucous  and 
salivary  glands,  of  some  kidney  tubules,  etc.  Stratified 
pavement  epnthelium  is  that  on  the  epidermis,  the 
epithelium  lining  the  cavity  of  the  mouth,  pharynx, 


Epithelium.  33 

and  oesophagus   in    man  and  mammals,  the  anterior 
surface  of  tlie  cornea,  etc. 

Functionally,  epithelium  can  be  classified  as  :  (a) 
tegmental — p.y.  tlie  epidermis  of  the  skin,  the  epithe- 
lium of  mucous  membrane  ;  (6)  as  secretory — e.g.  the 
epithelium  lining  tlie  alveoli  and  tubes  of  secreting 
glands,  the  liver,  the  kidney,  etc.;  (c)  sensory — e.g.  the 
epithelial-like  cells  forming  the  terminal  organs  of 
nerve  fibres — e.g.  in  the  retina,  in  the  organ  of  hearing 
(cochlea,  vestibule,  and  semicircular  canals  of  the 
internal  ear),  in  the  taste  buds,  in  the  olfactory 
membrane,  and  in  the  skin;  (':/)  forming  special  horny 
organs — e.g.  hairs,  nails,  the  horny  papillae  on  the  tongue 
of  feline  animals  ;  [e)  some  specific,  not  well-understood 
function — e.g.  the  epithelium  covering  the  glomeruli 
of  the  Malpighian  corpuscles  of  the  kidney,  the 
epithelium  (or  endothelium)  forming  the  wall  of  blood- 
capillaries  and  lymph  vessels. 

•Jl.  The  epidermis  (Fig.  25)  consists  of  the 
following  layers  : — («)  Stratum  corneum  :  this  is  the 
superficial  horny  layer,  and  it  consists  of  several 
layers  of  horny  scales,  without  any  nucleus.  Its 
layers  are  separated  from  one  another  by  narrow 
clefts  containing  air,  and  they  are  in  process  of  des- 
quamation. This  stratum  is  thickest  on  the  palm 
of  the  hand  and  fingers  and  the  sole  of  the  foot. 
(6)  The  stratum  lucidum,  composed  of  several  dense 
layers  of  horny  scales,  in  which  traces  of  an  ex- 
ceedingly flattened  nucleus  may  be  perceived, 
(c)  Then  follow  many  layers  of  nucleated  cells, 
forming  the  stratum  or  rete  Malpighii  or  rete 
mucosum.  The  most  superficial  layer  or  layers  of  it 
are  flattened  scales,  which  are  characterised  by  the 
presence  around  the  nucleus  of  globular  or  elliptical 
granules  of  the  nature  intermediate  between  pro- 
toplasm and  keratin.  Their  substance  is  called 
eleidin  by  Ranvier,  keratohyalin  by  Waldeyer  ;  these 

D 


34 


Elements  of  Histology, 


cells 
bans. 


form     the    stratura    granulosum    of     ^cv^.^ 


DeejDer    down,   the  cells    are 


Fi-.    25. 


a.  The  st 
c,  the 


—  From    a    Vertical    Section    tlirougli    the 
Epidermis.     {Atlas.) 

ratum  Malpiirhii ;  h.  tlie  Ptratuiu  ,trranulo>iiiii ; 
stratum  luciduiii  ;  d,  the  stratum  corneum. 


Laiiger- 
less  flattened 
and  more 
polyhed  r al , 
and  the  deepest 
form  a  layer  of 
more  or  less 
columnar  cells, 
placed  verti- 
cally on  the 
surface  of  the 
subjacent  co- 
rium. 

The  sub- 
stance of  the 
hairs,  nails, 
claws,  hoofs, 
consists      of 


horny  scales. 


{See  chapter   on   Skin.) 
22.   The 
pavement 
liiiiii    (Fig. 


Fig.  26. — From  a  Vertical  Section 
tliroiigh  the  anterior  layers  of  tlie 
Cornea.    (Handbook.) 

a.  The  stratified  pavement  eiiithelium; 
b,  the  substantia  propria,  with  the 
corneal  corpuscles  between  its  la- 
melht. 


Stratified 
epitlie- 

26)  lining 
the  cavity  of  the  mouth, 
the  surface  of  the  tongue, 
the  pharynx  and  oeso- 
phagus of  man  and  mam- 
mals, and  the  anterior 
surface  of  the  cornea, 
etc.,  is,  as  regards  tlie 
style  and  arrangement 
of  the  cells,  identical 
with  the  stratum  Mal- 
pighii  of  the  epidermis. 
The  cell  protoplasm  is 
more  transparent  in  the 
former,  and  the  granular 
cells     of     the      stratum 


Epithelium. 


35 


granulosum  are  not  always  present,  but  they  generally 
are  in  the  e})itheliiini  of  the  tongue  and  of  the  rest 
of  the  oral  ca^•ity.  The  most  superficial  scales  show 
more  or  less  horny  transformation. 

23.  Stratified  roliiiiiiiai'  €>|>itiic'iiiini  is  met 
with  on  the  lining  Hi('iiil)iane  of  the  respiratory 
organs  :  in  the  larynx,  trachea,  and  large  bronchi. 
It  consists  of  several  layers  of  columnar  cells  ;  a 
superficial  layer  of  conical  or  prismatic  cells,  with  a 
more  or  less  pointed  extremity  directed  towards  the 
depth ;  between  these  are  inserted  spindle-shaped 
cells,  and  finally  inverted  conical  cells. 

The  epithelium  of  the  ureter  and  bladder  is  called 
transitional  epitheUum.  It  is  stratified,  and  the  most 
superficial  layer  consists  of  j^olyhedral  cells.  Under- 
neath this  is  a  layer  of  club-shaped  cells,  between 
which  extend  one  or  more  layers  of  small  spindle- 
shaped  cells. 

Amongst  the  columnar  epithelial  cells  occurring  in 
man  and  mammals  the  ciliated  cells  and  the  gohlet 
cells,  and  amongst  the  squamous  cells  the  jirickle  cells, 
deserve  special  notice. 

24.  Ciliated  cells  are  characterised  by  possess- 
ing a  bundle  of  very  fine  longer  or  shorter  hairs  or 
cilia  on  their  free  surface.  These  cilia  are  direct 
prolongations  of  the  cell  protoplasm.  More  correctly 
speaking,  the  cilia  are  continuous  with  the  filaments 
or  striye  of  the  cell  protoplasm.  The  superficial 
layer  of  conical  cells  of  the  epithelium  in  the  respira- 
tory organs,  the  columnar  cells  lining  the  uterur,  and 
oviduct,  and  the  columnar  cells  lining  the  tubes  of 
the  epididymis,  possess  such  cilia.  In  lower  verte- 
brates the  ciliated  cells  are  much  more  frequently 
observed  ;  in  Batrachia  the  epithelial  cells  lining  the 
mouth,  pharynx,  and  (esophagus  are  ciliated. 

While  fresh  in  contact  with  the  membrane  which 
they  line,  or  even  after  removal  from  it,  provided  the 


36  Elements  of  Histology. 

cells  are  still  alive,  the  ciliated  cells  show  a  rapid 
synchronous  whip-like  movement  of  their  cilia,  the 
cilia  of  all  cells  moving  in  the  same  direction.  The 
movement  ceases  on  the  death  of  the  cell,  but  may 
become  slower  and  may  cease  owing  to  other  causes 
than  death,  such  as  coagulation  of  mucus  on  the 
surface,  want  of  sufficient  oxygen,  presence  of  car- 
bonic acid,  low  temperature,  etc.  In  these  circum- 
stances, removal  of  the  impediment,  as  by  dilute 
alkalies,  wdll  generall}^  restore  the  activity  of  the 
cilia.  Moderate  electric  currents  and  heat  stimu- 
late the  movement,  strong  electric  currents  and  cold 
retard  it.  Reagents  fatally  affecting  cell  protoplasm 
also  stop  permanently  the  ciliary  action. 

25.   CjJoblet  or  clialice  cells  (Figs.  24,  27)  are 

cells  of  the  shape  of  a  conical  cup.     The  pointed  part 

is  directed  away  from  the  free  surface,  and  contains  a 

compressed  triangular  nucleus  surrounded  by  a  trace 

of    protoplasm.     The    body    of  the 

=^="^-='^-%nn       goblet  contains  mucus.     This  latter 

P|'| -P<  £'  ^  -^' -  J      ^i"*^!   ^^    ^^  various   states    of    for- 

^llim^^^       mation,    and   may  at  any   time  be 

Fig.  27.— From  a  Ver-     poured    out    of    the    cell.       Goblet 

tical  Section  throucrh  n  ,  i  j.        •-! 

the  Epithelium  on     cclls  are  most  commonlv  met  with 
the  surface  of  the     amon^jst  the  epithelium  lining  the 

mucous     membrane  .  ^  ^  ,  ,  ^  ^ 

of  the  large  intes-     respiratory    Organs,   the   surface  01 
^'"^*  the    stomach    and    intestines,    and 

Three  goblet    cells   are  •    n  •  i         t  • 

seenpourin^'oiit their     especiallv     HI    mucous    glands,    m 

luucus.    TliG  r6st  urt*  "^  .  . 

ordinary     coiiuunar     whose    secretiuo-    portion    all    cells 

cells.  ®     '- 

are  goblet  cells. 
The  protoplasm  of  columnar  cells  facing  a  free 
surface,  no  matter  whether  in  simple  or  stratified 
epithelium,  ciliated  or  non-ciliated,  may  undergo 
such  alteration  as  will  lead  to  the  transformation  of 
the  cell  into  a  mucus-secretinfj  goblet  cell.  This 
takes  place  during  life,  and  corresjDonds  to  an  im- 
portant   function    of   columnar    ejDithelial    cells — viz. 


Epithelium.  37 

the  formation  of  iniicus.  In  mucus-secreting  glands 
all  the  epithelial  cells  have  this  function  permanently, 
but  in  ordinary  columnar  epithelium  only  a  compara- 
tively small  number  of  the  cells,  as  a  rule,  undergo 
this  change,  and  then  only  temporarily  :  for  a  cell 
subject  to  it  at  one  time  may  shorth^  afterwards 
resume  the  original  shape  and  aspect  of  an  ordinary 
protoplasmic,  cylindrical,  or  conical  epithelial  cell, 
and  vice  versa.  If  ciliyted  cells  undergo  this  change, 
the  cilia  are  generally  first  detached. 

It  can  be  shown  that  in  this  change  of  an 
ordinary  columnar  epithelial  cell  into  a  goblet  cell 
the  interstitial  substance  of  the  cell  reticulum  swells 
up  and  increases  in  amount,  the  meshes  enlarging  and 
distending  the  body  of  the  cell.  The  middle  and 
upper  part  of  the  cells  then  change,  tirst  into 
mucigen,  and  hnally  into  mucin,  which  is  eventually 
discharged,  leaving  in  the  deeper  part  the  compressed 
nucleus  surrounded  by  a  trace  of  protoplasm  behind 
(see  Fig.  34). 

2G.  Prickle  cells  (Fig.  25). — Amongst  the 
middle  and  deeper  la3^ers  of  the  stratified  pavement 
epithelium,  such  as  is  present  in  the  epidermis  and 
on  the  surface  of  the  oral  cavity  and  pharynx,  we 
meet  with  a  close,  more  or  less  distinct  and  regular 
striation,  extending  from  the  margin  of  one  cell  to 
that  of  each  of  its  neighbours,  by  means  of  fine 
transverse  short  fibrils  which,  passing  from  proto- 
plasm to  ])rotoplasm,  connect  the  surfaces  of  the  cells. 

27.  Pigmented  epithelial  cells — i.e.  epithelial  cells 
filled  with  black  pigment  pai'ticles  (crystals)  —  are 
found  on  the  internal  surface  of  the  choroid  and 
iris  of  the  eyeball. 

In  coloured  skins,  and  in  coloured  patches  of  skin 
and  mucous  membrane,  such  as  occur  in  man  and 
animals,  pigment  in  the  shape  of  dark  granules  is  found 
in  the  protoplasm  of  the  deeper  epithelial  cells,  as  well 


38  Elements  of  Histology. 

as  in  branched  cells  situated  between  the  epithelial 
cells  of  the  deeper  layers.  Minute  branched  non- 
pig  mented  nucleated  cells  are  met  with  in  the 
interstitial  or  cement  substance  of  various  kinds  of 
epithelium,  simple  and  stratified — e.g.  epidermis, 
epithelium  of  oral  cavit}',  cornea,  etc. 

28.  Epitlielial  cells  undergo  division,  and  by  this 
means  a  constant  regeneration  takes  place.  In  those 
parts  where  the  loss  of  the  superficial  layers  of  cells  is 
conspicuous,  such  as  the  epidermis,  the  stratified  epi- 
thelium of  the  tongue  and  oral  cavity,  the  sebaceous 
follicles  of  hairs,  the  regeneration  goes  on  more 
copiously  than  at  places  where  no  such  conspicuous 
loss  occurs — as,  for  instance,  in  the  stomach  and  in- 
testines, the  secreting  glands,  or  sense  organs. 

In  the  stratified  pavement  epithelium  it  is  the 
cells  of  the  deepest  layers  which  chiefly  divide.  As 
a  rule,  this  division  takes  place  transversely  in  the 
cylindrical  cells,  but  may  also  occur  longitudinally  (A. 
Kollmann).  The  epithelial  cells  next  to  the  deepest 
layer  of  columnar  cells  are  to  a  great  extent  the  result 
of  the  division  of  the  latter,  and  as  this  proceeds  there 
is  a  orradual  shiftino;  of  the  older  cells  towards  the 
surface  and  a  simultaneous  flattening  of  the  cell 
protoplasm  as  well  as  the  nucleus. 

29.  The  interstitial  substance  between,  and  the 
protoplasm  of,  the  epithelial  cells  being  a  soft  flexible 
material,  the  cells  can  change  their  shape  and  arrange- 
ment owing  to  pressure  exerted  on  them  by  the  con- 
traction or  distension  of  the  subjacent  membrane. 
Thus  the  epithelium  lining  a  middle-sized  bronchus 
at  one  time  apjDears  composed  of  thin  columnar  cells 
in  two  layers ;  at  another,  as  a  single  layer  ;  or  again, 
as  a  single  layer  of  short  columnar  cells  :  in  the  first 
case  the  bronchus  ig  contracted,  in  the  second  in  a 
medium  state  of  distension,  in  the  third  much  dis- 
tended.       Similar    changes   may  be    noticed    in    the 


Epithelium.  39 

epithelium     lining     tlu^     bladder    and     the,     stratum 
Malpighii. 

The  interstitial  substance,  being  a  soft,  semi-fluid 
substance,  represents  the  paths  through  whicli  granules 
and  formed  particles  may  find  their  way  from  the  free 
surface  into  the  membrane  beneath,  or  vice  versa. 
Also  leucocytes  pass  out  in  certain  localities  from  the 
membrane  underneath,  between  and  into  the  sul)stance 
of  epithelial  cells,  and  may  Anally  be  discharged  on  to 
the  free  surface — e.g.  in  the  tonsils,  in  the  fauces  and 
pharynx  and  larynx.  Epithelial  cells  may  in  this  way 
include  in  tlieir  substance  various  formed  particles  : 
granules,  fat  globules,  leucocytes,  nuclei  of  leucocytes, 
etc.  Besides  these  cell  enclosures  and  the  paranuclei 
and  chromatin  granules  mentioned  in  a  former  para- 
graph, in  some  localities  [e.g.  stratum  Malpighii  of  the 
ef)idermis,  epithelium  of  the  oral  cavity,  pharynx  and 
oesophagus)  the  epithelial  cell  substance  undergoes 
a  partial  or  total  change  into  keratinous  substance, 
keratohyalin,  forming  a  mantle  around  the  unchanged 
cell  j)rotoplasm  like  a  capsule. 


40 


CHAPTER    lY 


ENDOTHELIUM. 


30.  The  free  surfaces  of  the  serous  and  synovial 
membranes,  and  of  those  of  the  brain  and  spinal 
cord,  the  posterior  surface  of  the  cornea  and  anterior 
surface  of  the  iris,  the  surfaces  of  tendon  and  tendon- 
sheaths,  the  lymph  sinuses  or  lymph  sacs  of  amphibian 
animals,  the  cavity  of  the  heart,  of  blood-vessels 
and  of  lymphatic  vessels,  are  lined  with  a  continuous 
endothelial  membrane,  composed  of 
a  single  layer  of  flattened  trans- 
jjarent  squamous  cells,  called  endo- 
thelial cells  (Fig.  28).  Each 
contains  an  oval  nucleus,  situated 
as  a  rule  excentrically.  Just  as  in 
Fig  28 -Endothelium    the    case  of   epithelium,  "  the    endo- 

of  the  Mesentery  of       ■,■,•■>         n       i  ■    • 

Cat.  thelial  cell  plates  are  joined   by    a 

The  outlines  of  the  endo-    fluid  or  semi-fluid  liomoifeneous  in- 

thehal  cells  and  tlie  •    •    7  7 

nucleus  of  the  latter    terstitiat  or  Cement  substance  or  the 

are  well  shown.  „      ,    ,      , . 

nature  oi  globulin.  \\  hen  examin- 
ing any  of  the  above  structures  fresh,  the  endothelial 
cells  are  not,  as  a  rule,  visible,  owing  to  their  great 
transparency;  but  by  staining  the  structures  with  a 
dilute  solution  of  nitrate  of  silver,  and  then  exposing 
them  to  the  influence  of  the  light,  the  cement  sub- 
stance appears  stained  black,  whereby  the  shape  and 
size  of  the  cell  plates  become  e^■ident.  By  various 
dyes  also  the  nucleus  of  each  cell  plate  may  be  brought 
into  view. 

On    careful    examination,   and    with    suitable    re- 
agents,   it    can   be  shown  that   each    endothelial   cell 


En  DO  THELIUM. 


41 


consists  of  a  homogeneous  ground  'plate.  Tii  it  lies 
tlie  nucleus,  and  around  it  is  a  sul)staiicf*  which  ap- 
pears granular,  but  ^vhich  is  of  a  fibrillar  nature,  the 
fibril  he  being  arranged  in  a  network,  and  extending 


Fig.  20.— Network  of  Lymphatics  in  the  Central  Teudon  of  the  Diaphragm 
of  Rabbit,  prepared  with  nitrate  of  silver,  so  as  to  show  the  outlines  of 
the  Endothelial  Cells  formiug  the  wall  of  the  Lymphatics.  {Handbook.) 

a.  Large  I^-mphatic  vessels;  b,  Ivinphatic  capillaries  ;  c,  apparent  ends  of  the 

capillaries. 


in  many  places  up  to  the  margin  of  the  ground 
plate.  The  nucleus  is  limited  by  a  membrane,  and 
contains  a  well-developed  reticulum.  The  tibrillje  of 
the  cell  substance  appear  to  be  connected  with  the 
nuclear  reticulum. 

31.  As  regards  shape,  endothelial  cells  differ 
considerably.  Those  of  the  pleura,  pericardium,  peri- 
toneum, and  endocardium  of  man  and  mammals  are 


42 


Elemexts  of  Histology. 


more  or  less  polygonal,  or  slightly  elongated.  Their 
outlines  vary  ;  in  the  lining  of  the  lymph  sacs  of  the 
frog  they  are  much  larger,  and  of  very  sinuous  out- 
line ;  while  those  of  the  posterior  surface  of  the  cornea 


Fig.  30. — Onientum  of  Rabbit,  stained  with  Nitrate  of  Silver.    {Atlo.s.) 
(I.  Ordiuaiy  flat  endothelial  cells  ;  b,  germinating  cells. 


are  very  regular,  pentagonal,  or  hexagonal,  ha^^Ilg 
straight  outlines  in  the  perfectly  normal  and  well-pre- 
served condition,  but  serrated  and  sinuous  after  they 
have  been  prepared  with  various  reagents  and  in  the 
abnormal  state  ;  the  endothelial  plates  lining  the  blood- 
vessels and  lymphatic  vessels  (Fig.  29)  are  narrow 
and  elongated,  with  more  or  less  sinuous  outlines.  In 
the  lymphatic  capillaries  the  endothelial  plates  are 
polygonal,  but  their  outline  is  serrated. 

32.   As  a  rule,  the  endothelial  cells  are  flattened — - 


Endothelium. 


4: 


i.e.  scaly — but  in  some  places  they  are  polyhedral, 
or  even  short  columnar.  Such  cells  occur  isolated  or 
in  small  gi'oups,  or  covering  large  and  small  patches, 
nodular,   \illous,   or  cord-like  structures  of  the  pleura 


Fig.  31.— Part  of  Peritoneal  Surface  of  the  Central  Tendon  of  Diaphragm  of 
Rabbit,  prepared  with  Nitrate  of  Silver.     (Handbook.) 

s,  StoniRta;  Z,  lymph-channe!s  ;  f,  tendon  Inindles.    The  surface  is  covered  witli 
endothelium.'   The  stomata  are  surrounded  by  geruunatiug  endi)thelial  cells. 


and  omentum,  on  the  synovial  membranes,  tunica 
vaginalis,  testis,  etc.  They  are  especially  observable 
in  considerable  numbers  in  the  pleura  and  omentum 
(Fig.  30)  of  all  normal  subjects  (in  man,  ape,  dog,  cat, 
and  rodent  animals) ;  their  number  and  frequency  of 
occurrence  are  increased  in  pathological  conditions 
(chronic  inflammations,  tuberculosis,  cancer,  etc.). 

These  endothelial  cells  are  tlie  germinating  endo- 
thelial   cells,    and   they   can    be    shown    to    be    in  an 


44 


Elements  of  Histology. 


active  state  of  division.  They  thus  produce  small 
spherical  lymphoid  (amoeboid)  cells,  which  ultimately 
are  absorbed  by  the  lymphatics,  and  carried  into  the 
blood    system    as    white   1)1  ood   corjiuscles.      On    the 


Fi.£ 


-Part  of  Omentum  of  Cat,  stained  with  Nitrate  of  Silver. 


a,  Feuestraj  or  holes  ;  />,  tianecultB  covert-a  witli  emloilielium.    Ouiy  tiie  outliues 
(silver  lines)  of  the  endothelial  cells  are  shown. 


surface  of  the  serous  membranes,  especially  the 
diaphragm  (Fig.  31)  and  pleura,  there  exist  minute 
openings,  stomata,  leading  from  the  serous  cavity  into 
a  lymphatic  vessel  of  the  serous  membrane.  These 
stomata  are  often  lined  by  germinating  cells. 

33.  In  the  frog,  germinating  cells  occur  in  great 
abundance  on  the  mesogastrium  and  the  part  of  the 
peritoneum  which  separates  the  ])eritoneal  cavity 
from  the  cisterna  lymphatica  magna.      This  part  of 


Endothelium.  45 

the  peritoneum  is  called  the  septum  cisternae  lym- 
phaticji?  magnsB,  and  on  it  occur  numerous  holes  or 
stomata,  by  which  a  free  communication  is  established 
between  the  two  cavities.  On  the  peritoneal  surface 
of  this  septum  the  stomata  are  often  bordered  by 
germinating  cells.  In  th(^  female  frog,  these  and 
other  germinating  endothelial  cells  of  the  peritoneum 
(mesogastrium,  mesenterium,  septum  cisternee)  are 
ciliated. 

34.  The  omentum  and  parts  of  the  pleura  are,  in 
the  adult  human  subject,  ape,  dog,  cat,  guinea-pig,  rat, 
etc.,  of  the  nature  of  di.  fenestrated  membrane  {¥\g.  32), 
bands  of  fibrous  tissue  of  various  sizes  dividing  and 
reuniting,  and  leaving  between  them  larger  or  smaller 
holes,  in  shape  oblong  or  circular.  These  holes  or 
fenestras  are  not  covered  with  anything,  the  endo- 
thelial cells  adhering  only  to  the  surfaces  of  the 
bands  without  bridging  over  the  fenestrse.  On  the 
peritoneal  surface  of  the  diaphragm  the  endothelial 
cells  possess  a  different  arrangement  from  that  on 
the  pleural  side ;  on  the  former  surface  a  number  of 
lymph  channels  (that  is,  clefts  between  the  bundles 
of  tendon  and  muscle)  radiate  towards  the  middle  of 
the  central  tendon.  The  endothelium  of  the  free 
surface  over  these  lymph  channels  is  composed  of 
much  smaller  cells  than  at  the  places  between,  so 
that  the  endothelium  of  the  peritoneal  surface  of  the 
diaphragm  shows  numbers  of  radiating  streaks  of 
small  endothelial  cells.  Many  of  these  small  cells 
are  not  flattened,  but  polyhedral,  and  of  the  nature 
of  germinating  cells  (Fig.  31).  The  above-mentioned 
stomata  occur  amongst  these  small  endothelial  cells. 


46 


CHAPTER    Y. 

FIBROUS    CONNECTIVE    TISSUES. 

35.  By  the  name  of  "  connective  tissues "  we 
designate  a  variety  of  tissues  which  have  in  common 
with  one  another,  that  they  are  developed  from  the 
same  embryonic  elements ;  that  they  all  serve  as  sup- 
porting tissue  or  connecting  substance,  for  nervous, 
muscular,  glandular,  and  vascular  tissues  ;  that  they 
are  capable  of  taking  one  another's  place  in  the 
different  classes  of  animals  ;  that  in  the  embryo  and 
in  the  growing  normal  and  morbid  condition  one  may 
be  changed  into  the  other  ;  that  in  the  adult  they 
gradually  shade  off  one  into  the  other ;  and  that  they 
yield  allied  chemical  products. 

Connective  tissues  are  divided  into  the  three  great 
groups  of  (1)  fibrous  connective  tissue;  (2)  cartilage; 
(3)  bone,  to  which  may  be  added  dentine.  Each  of 
these  is  subdivided  into  several  varieties,  as  will 
appear  farther  on  ;  but  in  all  instances  the  ground 
substance,  or  matrix,  or  intercellular  substance,  is  to 
be  distinguished  from  tJie  cells.  In  the  fibrous  con- 
nective tissue  the  matrix  yields  collagen  or  gelatin, 
and  the  cells  are  called  connective-tissue  cells,  or  con- 
nective-tissue corpuscles.  In  the  cartilage  the  ground 
substance  yields  chonclrin,  and  the  cells  are  called 
cartilage  cells.  In  the  third  group  the  ground  sub- 
stance contains  inorganic  lime  salts,  intimately  con- 
nected with  a  fibrous  matrix,  and  the  cells  are  called 
hone  cells. 

36.  The  fibrous  coiiiiertivc  tissue,  or  white 
fibrous  tissue,    occurs    in    the    skin     and    mucous 


Fibrous  Connective  Tissues. 


Al 


membranes,  in  tlie  serous  and  synovial  membranes, 
in  tlie  membranes  of  the  brain  and  spinal  cord,  in 
tendons  and  tendon  sheaths,  in  fascite  and  aponeuroses, 
in  the  intermuscuhir  tissue,  and  in  the  tissue  con- 
nectino;  neiirhbourim'-  organs,  etc.  It  consists  of 
microscopic  band-like  or  cylindrical  bundles  or  fasciculi 
of  exceedingly  tine  homogeiuous  tinrils  (Fig.  33),  which 


Fig.  33. — Plexus  of  Bundles  of  Fibrous  Tissue  from  the  Oiuentuiu  of  Rat. 

«,  Capillary  blood-v'cSi'cl ;   ^,  lumiilc:^  nr  Hijidhs  tissue  ;   c  tue  oouuectivc-tiiiu.: 
foi'iuiscles;  c/,  i)lasiii  i  ceils.    {Atlas.) 

are  known  as  the  elementary  connective-tissue  fibrils. 
According  to  the  number  of  these  the  bundles  differ 
in  size.  The  bundles,  and  also  their  constituent 
fibrils,  may  be  of  very  great  length — several  inches. 
Where  the  fibrous  tissue  forms  continuous  masses — 
as  in  tendon,  fascia,  aponeurosis,  skin,  and  mucous 
membrane — the  microscoj)ic  bundles  are  aggregated 
into  smaller  or  larger  groups,  the  trabeciilce.,  and  these 
are  again  associated  into  groups.  The  fibrils  are  held 
together  by  an  albuminous  (globulin),  semi-fluid, 
homogeneous  cement  substance^  which  is  also  present 
between  the  bundles  forming  a  trabecula. 


48  Elements  of  Histology. 

The  groups  of  bundles,  and  even  the  individual 
bundles,  are  in  some  localities  invested  with  an  elastic 
sheath — e.g.  in  the  trabeculae  of  bundles  in  the 
subcutaneous  tissue. 

On  addincj  an  acid  or  an  alkali  to  a  bundle  of 
fibrous  tissue,  it  is  seen  to  swell  up  and  to  become 
glassy-looking,  homogeneous,  and  gelatinous.  Sub- 
jected to  boiling  in  water,  or  to  digestion  by  dilute 
acids,  the  bundles  of  tibrous  tissue  vield  collacjen  or 
gelatin. 

37.  According  to  the  arrangement  of  the  bundles, 
the  fibrous  connective  tissue  varies  in  ditierent  locali- 
ties. (1)  In  tendons  and  fasciae  the  bundles  are 
arranged  j^arallel  to  one  another.  (2)  In  the  true 
skin  and  mucous,  serous,  and  synovial  membranes,  in 
the  dura  mater  and  tendon  sheaths,  the  trabeculse  of 
bundles  divide  repeatedly,  cross  and  interlace  very 
intimately  with  one  another,  so  that  thereby  a  dense 
felt-work  is  produced.  (3)  In  the  subcutaneous,  sub- 
mucous, or  subserous  tissue,  in  the  intermuscular 
tissue,  in  the  tissue  connecting  with  one  another 
different  organs  or  parts  of  the  same  organ — i.e.  inter- 
stitial connective  tissue— the  texture  of  the  tibrous 
tissue  is  more  or  less  loose,  the  trabecul^e  dividing  and 
reuniting  and  crossing  one  another,  but  leaving  between 
them  larger  or  smaller  spaces,  celluhe  or  areola?,  so 
that  the  tissue  assumes  the  character  of  a  loose 
plexus,  which  is  sometimes  called  "  areolar  "  or  "  cel- 
lular tissue."  Such  tissue  can  be  more  or  less  easily 
separated  into  larger  or  smaller  lamelhie,  or  plates  of 
trabecul^e.  (4)  In  the  omentum  and  parts  of  the 
pleura  of  man,  ape,  dog,  cat,  and  some  rodents,  and 
in  the  subarachnoidal  tissue  of  the  spinal  cord  and 
brain,  the  trabecule  form  a  fenestrated  membrane,  with 
larger  or  smaller  oval  or  circular  holes  or  fenestra?. 

38.  The  eoiiiiective -tissue  cells  or  corpuscles 
occurring    in    white    fibrous    tissue    are    of    several 


F/niwus  C(hxXECTn'E  T/ssu/:s. 


49 


varieties,      {a)  lii  teiulon  and  faseiie  tlie  cells  ai<'  called 
tendon  cells  or  tendon  corpuscles  ;   they  are  flattened 


^-3^^ 


Fig.  34.— Tendon  of  Mouses  Tail.    (£.  A.  Schu/er.) 
a,  Chains  of  tendon-celJ!?  seen  broadways  ;  b,  the  same  in  profile. 


nucleated  protoplasmic  cells  of  a  square  or  oblong 
shape  (Fig.  34),  forming  continuous  rows  (single  files), 
situated  on  the 
surface  of  groups 
of  bundles  of 
fibrous  tissue. 
Between  these 
groups  are  wider 
or  narrower 
channels,  the  in- 
t  erf  CISC  i  culn  r 
lymph  spaces, 
running  parallel 
with  the  long 
axis  of  the  ten- 
don (Fig.  35). 
The  cells  in  each 
row  are  separ- 
ated from  one 
another  by  a  nar- 
row line  of  allju- 

minous   cement  substance,  and  the  round  nucleus  of 
the  cell  is    generally  situated  at  one   end,   in  such  a 


Fig.  3.J.  — From  a  Transveix-  Section  through  the 
Tendons  of  tlie  Tail  of  a  Mouse,  stained  with 
gold  chloride.     {Handbook.) 

Several  fine  tendons  are  shown  here.  The  darfe 
branched  corpnseies  correspond  to  albuminous 
cement  substance  stained  with  srold  chloride; 
they  are  the  channels  between  the  bundles  of 
fibrous  tissue,  constituting,'  the  tendon,  and  seen 
here  as  the  clear  spaces  in  cross  section.  In  each 
of  these  channels  is  a  row  of  tendon  cells— not 
discernible  here,  the  Ion?  axis  of  these  rows 
beins  parallel  with  the  long  axis  of  the  tendon. 


^o 


Elemexts  of  Histology. 


Fig.  36.— From  the  Tail  of  a  Tadpole. 

c.   Branched   coDnective  tissue  cells ;   m, 
a  migratory  cell.    (Atlas^ 


way  that  in  two  adjacent  cells  of  the  growing  tendon 
the  nuclei  face  each  other.  This  indicates  that  the 
individual   cells  undergo  division.     Corresponding  to 

the  martjin  of  each 
row,  the  cells  j;>ossess 
minute  processes.  The 
cell  plate  is  not  quite 
riat,  Ijut  possessed  of 
one,  two,  or  even 
three  membranous  pro- 
jections l)y  which  it 
is  wedged  in  between 
the  individual  bundles 
of  the  group  to  which  the  row  of  cells  belongs. 

39,   (fe)   In  the  serous  meuibranes,   cornea,   subcu- 
taneous tissue,  and  loose  connective  tissues,  the  cells 

are  flattened  transparent  cor- 
puscles, eac-li  witli  an  oblong 
flattened  nucleus,  and  more  or 
less  branched  and  connected  by 
tlifir  processes.  In  the  cornea 
they  are  spoken  of  as  the 
corneal  corpuscles,  and  are  ver}' 
richly  branched  (Fig.  37).  They 
are  situated  between  the  lamellae 
of  fibrous  bundles  of  which  the 
ground  substance  of  the  cornea 
consists. 

These    corpuscles    are    also 
situated    in  the    interfascicular 
lymph    spaces,    or    spaces    left 
between    the    bundles    of    the 
fibrous  matrix,  which  are   cavi- 
ties in   the  interstitial  cement, 
cementing  tlie   Imndles  and   trabecuke   together  (von 
Recklinghausen).     In    the    cornea    and    serous  mem- 
branes these  spaces    possess    the    shape  of    branched 


Fig.  37. — Fi-om  the  Cornea 
of  Kitten,  showing  the 
Networks  of  the  Branched 
Corneal  Corpuscles. 

a.  The  network  of  their  pro- 
cesses ;  b,  nucleus  of  the 
corpuscle.    (Atla^.') 


Fibrous  Conxecth'e  Tissues. 


51 


lymph 


V 


laciinne,  eacli  lacuna  being  the  home  of  the  body  of 
the  cell,  while  the  branches  or  canaliculi  contain 
its  processes.  These  canaliculi  form  the  channels 
by  which  neighbouring  lacuna?  anastomose  with  one 
another  (Fig.  38).  The  cell  and  its  processes  do  not 
fill  up  the  lacuna  and  its  canaliculi,  but  are  bathed 
in  the  paraplasma  or  fluid  contained  in  the 
canal    system.         In 

loose    connective  tis-      v^^':m^'''"'^'m 
sue    the  lacuna  may      "    ^  '^ 

be     of     considerable  7 

size,  and  may  contain 
several  connective 
cells,  which  make  as 
it  were  a  lining  for 
it.  These  in  some 
places  are  very  little 
branched,  and  almost 
form  a  continuous 
endotheloid  mem- 
brane of  flattened 
cells.  Such  is  the 
subepithelial  endotJie- 
lium  ofDehove,  occur- 
ring underneath  the 
epithelium  on  the 
surface  of  the  mucous 

membrane  of  the  bronchi,  bladder,  and  intestines. 
40.  (c)  In  the  true  skin  and  mucous  membranes 
the  connecti^'e-tissue  cells  are  also  branched  flattened 
corpuscles,  and  by  their  longer  or  shorter  processes 
are  connected  into  a  network  (Fig.  36).  Each 
cell  has  a  flattened  oblong  nucleus.  As  a  rule, 
some  of  the  processes  are  membranous  prolongations 
coming  ofl"  under  an  angle  from  the  body  of  the  cell, 
which  is  then  called  the  chief  plate,  the  processes 
being  the  secondarv  plates.      By  the  latter  the  cell  is 


g.  38.— From  the  Cornea  of  Kitten, 
stained  with  Nitrate  of  Silver,  show- 
ing the  Lymph-canal  System. 

fl.  The  lacuna?,  each  containiugthe  nucleated 
cell-body  just  indicated  here;  b,  the 
canaliculi  for  the  cell  procer^ses.  (Atlas.') 


52  Klemexts  of  Histology. 

wedged  in  between  the  bundles  of  the  trabecula  to 
which  it  belongs. 

This  character  of  the  cells  (i.e.  possession  of 
secondary  j)lates)  is  well  shown  Ijy  the  cells  of  the 
skin  and  mucous  membranes,  but  only  in  a  very 
limited  degree  by  those  of  the  cornea  and  serous  mem- 
branes, and  somewhat  better  by  some  of  those  of  the 
subcutaneous  and  other  loose  connective  tissues. 

In  the  skin  and  mucous  membranes  also  the  cells 
and  their  processes  are  bathed  in  the  paraplasma 
contained  in  the  interfascicular  lymph  spaces. 

41.  The  connective  -  tissue  corpuscles  hitherto 
mentioned  are  fixed  corpuscles  :  they  do  not  show 
movement.  Kiihne  and  Rollett  ascriVje  to  the  corneal 
corpuscles  a  certain  amount  of  contractility,  inasmuch 
as  they  are  said  to  be  capable  of  withdrawing  their 
processes  on  stimulation.  When  this  ceases  they 
are  said  again  to  protrude  them.  According  to 
Strieker  and  Norris,  they  acquire  contractility  when 
the  corneal  tissue  is  the  seat  of  inflammatory 
irritation.  It  can  be  shown  that  the  connective- 
tissue  cells  consist,  like  the  endothelial  plates, 
of  a  ground  plate  and  a  fibrillar  reticulated  (granular- 
looking)  substance  around  the  nucleus,  and  extending 
beyond  the  ground  plate  into  the  proces.ses  of  the 
cell. 

42.  Pigment  cells. — In  the  cold-blooded  verte- 
brates, fishes,  reptiles,  and  amphibian  animals,  we 
find  certain  branched  nucleated  connective-tissue  cor- 
puscles, distinguished  by  their  size  and  by  the  proto- 
plasm both  of  the  cell-body  and  processes  (but  not  of 
the  nucleus)  being  filled  with  pigment  granules.  The 
pigment  is  either  grey  or  yellow,  or  more  commonly 
dark  brown,  or  even  black.  These  cells  are  called  pig- 
mented connective-tissue  cells,  or  simply  inijinent  cells. 
They  are  very  numerous  in  the  skin  of  fishes,  reptiles, 
and  amphibian  animals,  and  also  around  and  between 


Fibrous  Connective  Tissues. 


53 


the  blood-vessels  of  the  serous  membranes.  They  are 
also  present  in  man  and  mammals,  but  then  they  are 
chieriy  linuted  to  the  eye-ball,  where  they  occur  in  the 


Fig.  89,— Pigment  Cells  of  the  Tail  of  Tadpole. 

A,  B,  c,  D  represent  variims  states ;  a  heinar  a  cell  in  an  uncontracted  or  passive 
stati'.  D  in  a  contracied  or  active  state. 

proper  tissue  of  the  iris  of  all  but  albino  and  bright 
blue  eyes,  and  in  the  tissue  of  the  choroid  membrane. 
In  dark  eyes  of  mammals  a  large  number  of  these 
cells  are  found  in  the  tissue  between  the  sclerotic  and 
choroid,  as  the  lamina  fusca,  and  also,  but  to  a  more 


54  Elemexts  of  Histology. 

limited  degree,  in  the  sclerotic.  As  a  rule,  they  appear 
to  be  of  various  kinds  :  sucli  as  are  flattened,  large 
plates  perforated  l>y  a  number  of  small  and  large  holes 
and  minute  clefts  :  such  as  possess  a  more  spindle- 
shaped  liudy.  and  loni'.  thin,  not  very  richly  branched 
processes  :  and  intermediate  forms  between  the  two. 
But  on  careful  examination  it  will  be  seen  that  these 
appearances  are  due  to  different  .states  of  contraction 
of  the  same  kind  of  cells  (Fig.  39). 

43.  In  the  lower  vertebrates  the  dark  pigment 
cells  show  marked  contractility,  ina^mucli  as  they  are 
capable  of  altogether  withdrawing  into  their  body  the 
pigmented  processes.  Tn  the  passive  state  these  are 
exceedino'lv  numerous,  anrl  form  a  network  so  dense 
that  the  whole  mass  of  the  cells  and  their  paraplasma 
resembles  an  extremely  close  network  of  pigment. 
In  tlie  maximum  of  activity  the  pigmented  processes 
disappear,  being  withdrawn  into  the  cell-body,  which 
now  looks  like  a  spherical  or  oblong  mass  of  black 
pigment.  Between  the  states  of  passiveness  and 
maximum  activity  there  are  various  intermediate 
grades,  in  which  the  pigmented  processes  are  of 
various  numbers  and  lengths. 

41.  Owing  to  the  great  number  of  the  pigment 
cells  in  the  skin  of  fishes  and  amphibians,  the  state 
of  contraction  of  these  cells  materially  affects  the 
colour  of  the  skin.  If  the  dark  pigment  cells  of  a 
particular  part  contract,  the  skin  of  this  jiarticular 
part  will  1)ecome  lighter  and  brighter,  the  degree  of 
liijhtness  and  brightness  depending  on  the  degree  of 
contraction  of  the  pigmented  processes  by  the  cells. 
Briicke  has  shown  that  darkne.ss  is  a  stimulus  to  the 
pigmented  cells  :  they  contract  and  the  skin  becomes 
lifdit.  Sunlidit  leaves  the  piomented  cells  in  the 
pas.sive  state,  their  pigmented  processes  numerous 
and  well  branched,  and  the  skin  appears  therefore 
of  a  darker  colour.      If   previously    they    have  been 


Fibrous  Coxnective  Tissues. 


55 


contracted  by  darkness,  on  being  exposed  to  sunlight 
they  again  return  to  tlie  passive  state.  Tlie  contrac- 
tion of  the  pigment  cells  is  under  the  direct  influence 
of  the  nervous  system  (Lister).  Pouchet  proved  that 
the  contractility  of  the  pigment  cells  of  the  skin  of 
certain  fishes  is  intiuenced  as  a  reflex  action  by  the 
stimulation  of  the  retina  by  light. 

45.  Fat    cells. — Fat   cells    in    the    ripe    and 
fully-formed   state   are  spherical,  large  vesicles,  each 


Fig.  40. — From  a  Preparation  of  the  Omentum  of  Guiuea-pig.     {Atlas.) 
a,  Artery  ;  v,  vein  ;  c,  young  capillary  lilooil-vesriel ;  d,  fat  ceils?. 

consisting  {a)  of  a  thin  protoplasmic  membrane,  which 
at  one  point  includes  an  oval  nucleus  flattened  from  side 
to  side,  and  (/>)  of  a  substance,  which  is  a  fat  globule 
filling  the  cavity  of  the  vesicle  (Fig.  40).  These  fat 
cells  are  collected  together  by  fibrous  connective 
tissue  into  smaller  or  larger  groups,  which  in  their 
turn  form  lobules ;  these  again  form  by  means  of 
thicker  masses  of  fibrous  connective-tissue  lohes,  and 
these  are  finally  arranged  as  continuous  masses.  Each 
group  and  lobule  has  its  afferent  arteriole,  one  or  two 


56  Elemexts  of  Histology. 

efferent  veins,  and  a  dense  network  of  capillaries 
between  ;  each  mesh  of  the  capillary  network  holding 
one,  two.  or  three  fat  cells  [see  below).  Such  are  the 
nature  and  arrangement  of  fat  or  adipose  tissue  in 
the  subcutaneous  and  sul)mucous  tissue,  in  the  serous 


Fig.  41. — From  a  Section  through  the  adipose  layer  of  the  Skin  ;  showing 
Lobules  of  Fat-cells.  Magnifying  jiower,  40.  {From  a  Photograph  by 
Mr.  A.  Pringle.) 

and  synovial  membranes,  in  the  intermuscular  tissue, 
in  the  loose  tissue  connecting  organs  or  parts  of 
organs. 

It  can  be  shown  that  fat  cells  are  derived  from 
ordinary  connective  tissue  cells.  In  some  places — 
both  in  the  embryo  and  adult — the  protoplasm  of  the 
connective-tissue  corpuscles,  growing  in  size,  becomes 


Fibrous  Connective  Tissues. 


SI 


tilled  with  small  fat  globules,  wliicb,  increasing  in 
number,  become  fused  with  one  another  to  larger 
globules  ;  as  their  size  thus  increases  the  cell  nucleus 
becomes  shifted  to  the  periphery ;  ultimately  one 
larijje  fat  globule  tills  the  cell,  and  what  is  left  of  the 


Fig.  42. — From  a  Section  of  Lobules  of  Fretal  Fat,  showing  connective-tissue 
septa  with  vessels  (surrounding  the  lobules)  ;  the  spheroidal  young 
cells,  many  of  them  containing  globules  of  fat.  {Photograph,  moderately 
magnified.) 

cell  protoplasm  surrounds  this  fat  globule  like  a  mem- 
branous envelope.  The  cell  as  a  whole  has  become  in 
this  process  many  times  its  original  size  (Fig.  41). 

46.  It  can  also  be  shown  that  where  at  one  time 
only  few  isolated  connective-tissue  corpuscles  are 
present,    at    another    time,   in    the    natural   state  of 


58  Elemexts  of  Histology. 

growth,  and  especially  under  very  fav-ourable  con- 
ditions of  nutrition,  the  connective-tissue  cells  become 
increased  by  cell-multiplication  so  as  to  form  groups  ; 
these  groups  continue  to  increase  in  size  and  to  be 
srraduallv  furnished  with  their  own  svstem  of  blood- 
vessels  ;  the  individual  cells  constituting  the  group 
become  then  converted  into  fat  cells,  and  their  pro- 
cesses are  thereby  lost  (Fig.  42). 

Isolated  connective -tissue  cells  situated  in  the 
neighbourhood  of  small  blood-vessels  are  converted 
into  fat  cells  under  favourable  conditions  of  nutrition. 

In  starvation  the  fat  cells  lose  their  fat  globule, 
tliey  become  smaller  and  contain  a  serous  fluid,  which 
may  ultimately  also  disappear.  Finally,  the  fat  cell 
may  be  reduced  to  a  small,  solid,  ^protoplasmic,  slightly 
branched  cell. 

47.  In  many  places  the  fibrous  connective  tissue 
includes,  besides  the  fixed  cells,  others  which  show 
amoeboid  movement,  u-andering  cells.  These  are  of 
various  kinds,  like  tliose  of  the  blood  :  (1)  A  majority 
are  identical  with  the  typical  hyaline  leucocytes  of 
thf-  blood,  as  regards  size,  shape,  aspect,  and 
general  nature  (Fig.  36,  m).  They  wander  about 
through  the  spaces  of  the  fibrous  tissue.  They  con- 
tain two  or  tViree  nuclei.  (2)  Those  of  the  second 
varietv  possess  a  small  amount  of  protoplasm,  and  one 
comparatively  large  nucleus  :  they  correspond  to  the 
lymplwcytes  mentioned  in  connection  with  the  white 
blood  corpuscles.  The  amoeboid  movement  of  these 
cells  is  not  so  distinct  as  in  the  first  variety.  (3) 
Plasma  cells  of  Waldeyer.  They  are  larger  than  the 
former,  less  prone  to  migrating,  being  possessed  of 
only  slight  amceboid  movement,  which  is,  however, 
sutiiiciently  pronounced  to  be  detected.  They  always 
contain  granules,  and  correspond  to  the  granular  cells 
mentioned  of  the  blood  :  also  in  regard  to  their  predi- 
lection for  acid  and  basic  aniline  dyes   they  may  be 


Fibrous  Connective  Tissues.  59 

distinguished  as  eosinopliile  or  oxypliile,  basophile 
or  neutropliile  cells.  The  "grnnules"  in  some  of 
the  plasma  cells  may  change  into  fat  globules,  and 
thus  the  plasma  cell  becomes  convei-ted  into  a  fat 
cell. 

48.  The  wandering  cells  occur  almost  in  all  loose 
fibrous  tissues,  chiefly  around  or  near  blood-vessels ; 
they  are  not  numerously  met  with  in  the  healthy 
state,  but  increase  greatly  in  the  state  of  inflamma- 
tion of  the  part.  Those  of  the  larger  kind — e.g.  the 
granular  wandering  cells  or  plasma  cells,  are  met  with 
in  certain  localities  onlv  ;  in  the  sub-linijual  orland  of 
the  dog  and  guinea-pig  they  occur  in  numbers  between 
the  gland  tubes  or  acini.  They  are  also  found  in  the 
mucous  membrane  of  the  intestine,  in  the  trabecular 
of  the  lymphatic  glands,  and  in  the  omentum.  The 
"  granules "  of  these  cells  under  many  conditions 
change  into  fat  globules.  Just  like  the  hyaline 
leucocytes  of  the  blood  so  also  those  of  the  connective 
tissues  are  capable  of  swallowing  minute  particles  of 
extraneous  matter — granules  of  living  (bacteria)  and 
non-living  matter  that  accidentally  find  entrance  into 
the  connective  tissue.  These  cells,  when  acting  in 
this  capacity,  are  called  pliagocytes. 

49.  Development  of  fibrous  tissue. — Fibrous 
connective  tissue  is  developed  from  embryonic  connec- 
tive-tissue cells — i.e.  from  spindle-shaped  or  branched 
nucleated  protoplasmic  cells  of  the  mesoblast.  The 
spindle-shaped  cells  are  met  with  isolated  or  in 
bundles,  as  in  the  umbilical  cord  or  embryonic  tendon. 
The  branched  cells  form  a  network,  as  in  the  foetal 
skin  and  mucous  membrane.  In  both  instances  the 
p)'otoplasm  of  the  embryonic  connective-tissue  cells 
increases  rapidly  in  amount,  and  becomes  gradually 
transformed  into  a  bundle  of  elementary  fibrils,  with 
a  granular-looking:  interstitial  substance.  The  nucleus 
of  the  original  cell  finally  disappears,      A  modification 


6o 


Elements  of  Histology. 


of  this  is  when  only  part — generally  unilateral — of 
the  cell  substance  is  converted  into  a  bundle  of  con- 
nective tissue  tibrils  and  inter-fibrillar  cement  sub- 
stance. A  remnant  of  the  protoplasm  persists  with 
the  nucleus  as  a  connective-tissue  cell. 

The  same  modes  of  formation  of  connective  tissue 
may  be  also  observed  in  the  achilt  under  normal  and 
pathological  conditions. 

50.   Fibrous    connective    tissue  is  in  most    places 

associated  with 
elastic  fibres  or 
yellow  elastic 
tissue.  These 
are  of  bright 
aspect,  of  vari- 
able thickness 
and  length, 
branching  and 
anastomosing  so 
as  to  form  net- 
works (Fig.  43). 
They  are  some- 
times straight, 
but  more  often 
twisted  and 
coiled.  The 
latter  condition 
maybe  observed 
when  the  tissue 
is  shrunk,  the  former  when  it  is  stretched.  They  do 
not  swell  up  in  acids  or  alkalies,  nor  yield  gelatin 
on  boiling,  but  contain  a  chemically  ditferent  sub- 
stance— viz.  elastin.  When  broken  their  ends 
generally  curl  up. 

51.  Elastic  fibres  occur  in  great  numbers  as  net- 
works extending  on  and  between  the  bundles  of  tibrous 
tissue    in   the   skin   and   mucous   membranes,   in  the 


-From  a  Prei>aration  of  the  Mesentery. 

of  fibrim-;  tissue;  h,  networks  of  elastic 
fibres.    {Atlas.') 


F/BKOus  Connect  I  \'E  Tissues.  6i 

serous  and  synovial  membranes,  and  in  tlie  loose  in- 
terstitial connective  tissues.  They  are  not  very  com- 
monly met  with  in  tendons  and  fasciae  ;  in  the  former 
they  are  seen  as  single  fibres  often  twisting  round  the 
tendon  bundles. 

Elastic  fibres  forming  bundles,  l)ut  branched  and 
connected  into  networks  within  the  bundle,  are  to  be 
found  in  large  numbers  in  the  walls  of  the  trachea, 
l)ronchi,  infundibula,  and  alveoli  of  the  lung,  in  the 
ligamenta  flava,  in  the  ligamentum  nucha?  of  the  ox 
(in  which  the  fibres  are  exceedingly  thick  cylinders), 
in  yellow  elastic  cartilage  {see  below),  in  tlie  mem- 
brane lining  the  cavity  of  the  heart,  and  in  the 
vascular  system,  particularly  the  arterial  division. 
In  the  latter  organs  the  intinia,  and  also  to  a  great 
extent  the  media,  consist  of  elastic  fibrils  densely 
connected  into  a  network. 

52.  The  following  are  special  morphological  modi- 
fications of  the  elastic  fibres  :  (o)  elastic  fenestrated 
membranes  of  Henle,  as  met  with  in  the  intima  of 
the  big  arteries ;  these  are  in  reality  networks  of 
fibres  with  very  small  meshes,  and  the  fibres  unusually 
broad  and  Hat.  {h)  Homogeneous  elastic  membranes, 
which  surround,  as  a  delicate  sheath,  the  connective- 
tissue  trabecules  in  some  localities  — e.^.  subcutaneous 
tissue,  (c)  Homogeneous-looking  elastic  membranes 
iu  the  cornea,  behind  the  anterior  epithelium  as  Botv- 
'nianHs  anterior  elastic  membrane,  and  at  the  back  of 
the  cornea  as  elastica  posterior,  or  Descemet's  mem- 
brane;  in  the  latter  bundles  of  minute  fibrils  haA'e 
been  observed.  Between  the  mucosa  and  submucosa 
of  the  stomach  of  the  cat  occurs  an  elastic  membrane 
of  considerable  thickness,  (d)  Elastic  trabeculae  form- 
ing a  network,  as  in  the  ligamentum  pectinatum  iridis. 
In  the  embryonic  state  the  elastic  fibres  are  nucleated, 
the  nuclei  beincj  the  last  remnants  of  the  cells  from 
which  the  fibres  develop,   one  cell    generally  giving 


0  2  Elements  of  Histology. 

oricjiii  to  one  fibre.     These  nucleated  fibres  are  called 
Henle's  nucleated  fibres. 

53.  Special  varieties  of  fibrous  connective  tissue 
are  these  : — 

(1)  Adenoid  retlcidum.  This  is  a  network  of  fine 
fibrils,  or  plates,  forming  the  matrix  of  lymphatic  or 
adenoid  tissue.  {!See  Lymphatic  glands.)  The  reti- 
culum is  not  fibrous  connective  tissue  nor  elastic 
tissue ;  it  contains  nuclei  in  the  young  state,  and  is 
derived  from  a  network  of  branched  cells  ;  but  in  the 
adult  state  the  reticulum  itself  possesses  no  nuclei. 
Those  found  on  it  do  not  form  an  essential  part  of  it. 

(2)  The  iiearogUa  of  Virchow  is  a  dense  network 
of  very  fine  homogeneous  fibrils  which  form  the  sup- 
porting tissue  for  the  nervous  elements  in  the  central 
nervous  system.  These  fibrils  are  supposed  to  be 
elastic  fibres  (Gerlach).  Embedded  in,  and  inti- 
mately connected  with,  the  network  of  these  fibres 
are  found  branched,  nucleated,  flattened  cell  plates, 
which  correspond  to  the  fixed  connective-tissue  cells. 

(3)  Gelatinous  tissue.  This  occurs  chiefly  in  the 
embiTO,  being  the  unripe  state  of  fibrous  connective 
tissue  (see  above).  It  consists  of  spindle-shaped  or 
branched  connective-tissue  cells,  separated  from  one 
another  by  a  homogeneous  transparent  mucoid  sub- 
stance. It  is  met  with  in  the  umbilical  cord  and 
ill  tlie  cavity  of  the  middle  ear  of  the  embryo,  and  in 
all  places  Avhere  fibrous  connective  tissue  is  to  be 
developed.  After  birth  it  is  found  in  the  tissue  of 
the  pulp  of  the  teeth,  where  it  persists  through  life ; 
in  some  places  it  is  the  precursor  of  fat  tissue,  its  cells 
becoming:  transformed  into  fat  cells. 


63 


CHAPTER    YI. 

CARTILACiE. 

54.  Cartilage  consists  of  a  firm  ground  sub- 
stance which  yields  diondrin,  and  of  cells  embedded 
in  it.  Most  cartilages  (except  on  the  articulating 
surface)  are  covered  on  their  free  surface  with  a 
membrane  of  tibrous  connective  tissue  with  a  few 
elastic  fibrils.  This  membrane  is  supplied  with 
blood-vessels,  lymphatics,  and  nerves,  and  is  of 
essential  imjiortance  for  the  life  and  growth  of  the 
cartihige.  This  is  the  perichondriiun.  There  are 
three  varieties  of  cartila^je. 

55.  (1)  Hyaline  cartila§:e(Fig.  44).— This  occurs 
on  the  articular  surfaces  of  all  bones ;  on  the  borders 
of  many  short  bones  ;  in  the  sternal  part  of  the  ribs, 
as  costal  cartilages :  at  the  margin  of  the  sternum, 
scapula,  and  os  ileum  :  in  the  rings  of  the  trachea, 
the  cartilages  of  the  bronchi,  the  septum  and  lateral 
cartilages  of  the  nose  ;  and  in  the  thyroid  and  cricoid 
cartilages  of  the  larynx.  The  ground  substance  is 
hyaline — i.e.  transparent,  like  ground  glass,  and  firm. 
The  cells  are  spherical  or  oval  proto^^lasmic  corpuscles, 
each  with  one  or  two  nuclei.  They  undergo  division, 
and  although  the  two  offsprings  are  at  first  close 
together  (half  moon-like  in  optical  section),  they 
gradually  grow  wider  apart  by  the  deposit  of  hyaline 
ground  substance  between  them.  The  cells  are  con- 
tained in  cavities,  called  the  cartilage  lacunce.  Each 
cell  generally  occupies  one  lacuna,  but,  according  to 
the  progress  of  division,  a  lacuna  may  contain   two. 


64 


Elemexts  of  Histology. 


four,  six,  or  eight  cartilage  cells  :  the  latter  are  those 
cases  in  which  division  proceeds  at  a  more  rapid  rate 
than  the  deposition  or  formation  ot  hyaline  ground 
substance  between  the  cells. 

The  jjart  of  the  cartilage  next  to  the  perichon- 
drium shows  most  active  growth;  hence  the  cells  are 
here  smaller,  closer  together,  and  there  is  less  ground 
substance. 

Each  lacuna  is  liner]  liy  a  delicate  membrane,  and, 
according  to  the  state  of  the  cell,  is  either  completely 

or  partially  filled  out  bv 
it.  This  membrane  is 
called  the  capsiiIe(Fig.  44). 
In  many  cartilages,  espe- 
cially in  growing  cartilage, 
it  is  thickened  by  the  ad- 
dition of  a  layer  or  layers 
of  hyaline  ground  sub- 
stance. This  is  the  most 
recently-formed  j^art  of 
the  matrix;  it  stains  differ- 
ently with  dyes,  and  is  dis- 
tinct from  the  older  part 
of  the  ground  substance. 

56.  In  some  places,  especially  in  articular  carti- 
lage (Tillmanns  Baber),  bundles  of  fine  connective- 
tissue  lil>rils  may  Ije  noticed  in  the  hyaline  ground 
substance. 

57.  In  some  cartilages  the  protoplasm  of  the  cell 
becomes  filled  with  fat  globules  (Fig.  46).  This  fact 
may  be  observed  in  many  normal  cartilages ;  some- 
times the  fat  globules  become  c(mfluent  into  one  larjje 
drop,  and  then  the  cell  has  the  appearance  of  a  fat 
cell.  In  old  age,  disease,  and  deficient  nutrition  lime 
salts  are  deposited  in  the  ground  sul)stance,  beginning 
from  the  circumference  of  the  cell.  The  earthy  matter 
a])})ears  in  the  shape  of  opaque  granules,  or  irregular 


Fig.     44.— Hyaline   Cartilage    of 
Hixiiian  Trachea. 

In  the  hyaline  ground  substance  are 
seen  the  cartilage  cells  enclosed  in 
capsules. 


Cartilage. 


or  anujular  granult's.      Tlie  groiincl  suljstance  thereby 
loses  its  transparency,  becomes  o})H<jue  in  transmitted, 
white      in     re- 
flected,     light, 

and,  of  course,  / 

ver}^  hard  and 
brittle.  This 
process  is  the 
calcification  of 
cartilage.  It  is 
also  met  with 
in  cartilage 
that  is  to  be 
replaced  by 
bone,  being  the 
precursor  of  the 
formation  of 
bone,  as  in  the 
€mbr3'0  {see  be- 
low), and  at  the 


Fit 


45. — From    a    Preparation    of  the    Sterna 
Cartilage  of  a  Newt. 


growing  ends  of 


The  lacunae  containing  the  cartilage  cells  anastomose 
by  tine  channels. 


I.  •',•-•5 


long  bones. 

58.   The   division  of  the  nucleus  of  the  cartilage 
cells  has  been  observed  during  life  by  Schleicher  and 
Flemming.     It  takes  place  after  the 
mode  of  karyokinesis.      The  lacunie  _<«U.,/  , 

of  the  cartilage  are  not  isolated 
cavities,  but  are  connected  with  one 
another  by  fine  channels  (Fig.  45), 
so  that  the  ground  substance  is 
easily  permeable  by  the  current  of 
nutritive  fluid.  These  channels  and 
lacunae  form  an  intercommunicating 
system,  and  are  connected  with  the 
lymphatics  of  the  perichondrium 
(Budge).  Formed  matter,  as  pig- 
ment granules,  red  and  white  blood 


Fig.  40.— Three  Car- 
tilage Cells  filled 
with  Fat  Droplets. 
From  the  hyaline 
cartilage  of  the 
nasal  septum  of 
Guinea-pig. 


66 


Elements  of  Histology. 


a,  o"  o::S, 


o 


corpuscles,  and  pus  corpuscles,  may  also  find  its  way 
into  the  channels  and  lacunae  of  the  cartilage  from 
the  perichondrium. 

At  the  borders  of  articular  cartilage,  where  this 
is  joined  to  the  synovial  meml)rane  and  to  the  capsule 
of  the  joint,  the  cartilage  cells  are  more  or  less  branched, 
and  pass  insensibly  into  the  branched  connective  tissue 
cells  of  the  membrane.  In  fcetal  hvaline  cartilacre 
many  of  the  cells  are  spindle-shaped  or  branched. 

59.  Ju  the  cartilage  separating  the  bone  of  the 
apophyses  from  the  end  of  the  diapbysis  of  tubular 
bones  there  is  a  peculiar  hyaline  cartilage,  known  as 
the  intermediate  or  ossifying  cartilage.  Its  cells  are 
arranged    in    characteristic    vertical    rows,   owing    to 

the  continued  division 
^11  ,jg     of  the  cells  in  a  trans- 

verse direction. 

Cartilages,  or  parts 
of  cartilages,  in  which 
the  cells  are  very 
closely  placed,  owing 
to  tlie  absence,  or 
scanty  deposit  and 
formation,  of  ground 
substance,  are  called 
jKi.rencliyiiiatous  or  cel- 
hdar  cartilacje. 

60.  (2iFibro-car- 
tilagre.  or  connective- 
tissue  cartilage,  occui-s 
as  the  intervertebi-al 
discs,  as  the  inter- 
articular  cartilages,  sesamoid  cartilages,  and  as  the 
cartilat{e  forminc(  the  marmn  of  a  fossa  »lenoidalis. 
It  consists  of  fibrous  connective  tissue  arranged  in 
hundles,  and  these  again  in  layers.  The  ground  sub- 
stance of  this  cartilage  is  said  to  yield  chondrin  and 


0 


■O 


O 


^  <S     Q  ^ 


o. 


€/^ 


^ 


•  Fig.  47. — Fibro-Cartilage  of  an  Inter- 
vertebral Ligament.    {Atlas.) 

Showing  the  bundles  of  fibrous  tissue  and 
rows  of  cartilage  cells. 


Cartilage.  67 

not  gelatin.  Between  the  strata  of  the  fibrous  bundles 
are  rows  of  more  or  less  flattened  oval  protoi)lasmic 
nucleated  cells,  each  invested  in  a  deticate  capsule 
(Fig.  47).  They  are  less  flattened  than  the  cells  of 
tendon,  and  the  capsule  dis- 
tinguishes the  two.   Where 

fibro-cartilage    passes    into    %^^    ^^     ^ ;  -«»^5-C7 
tendinous  tissue    the    two    WC 
kinds   of  cells  pass  insen-     if^ 
sibly  into  one  another.  5^^^^M_ 

61.      (3)    Yellow,   or     ^iS^^K^i?) 
ela«>tic  cai'tilag:e.     this     ^ji^?^?r^i^K:''^ii^^^o 
variety  is  also  called  reti-      ^p ''^-^^^^^^i 
cular  ;  it  occurs  in  the  epi-       •^,  ^^.;''®^^  TO 
glottis,  in  the  pinna  of  the        ^  -■--«--—.    ^ 
external  ear,    in    the   Eus- 
tachian   tube,    in  the  car- 

tilacrps     of     AVn\bp7-rr      and    ^ig.  4S.— From  a  Section  through 

iiiages    or  »  iisueig    ana  the  Epiglottis.  {AtUs.) 

Santorini     in      the     larynx.    «^    perichondrium;    &,    networks    of 

In  the  early  stages  this  eig^c^fltois  sun-ounding  the  car- 
kind  is  hyaline.     Gradually 

numbers  of  elastic  tibrils  make  their  appearance, 
growing  into  the  cartilage  matrix  from  the  peri- 
chondrium in  a  more  or  less  vertical  direction,  and 
branching  and  anastomosin^r  with  one  another.  The 
final  stage  is  reached  when  the  ground  substance  is 
permeated  by  f/^e/ise  neiicorJxs  of  elastic Jibrils  (Fig.  48), 
so  arranged  that  spherical  or  oblong  spaces  are  left, 
each  of  which  contains  one  or  two  cartilage  cells, 
surrounded  by  a  smaller  or  larger  zone  of  hyaline 
ground  substance. 


68 


CHAPTER     VII. 

BONE. 

62.  BoxE,  or  osseous  substance,  is  associated  with 
several  other  soft  tissues  to  form  a  bone  in  the  ana- 
tomical sense  of  the  word. 

(a)  The  periosteiiiii. — Except  at  the  articular 
surfaces,  and  where  bones  are  joined  with  one  another 
bv  liiraments  or  cartilao;e,  all  bones  are  covered  with  a 
vascular  membrane  of  fibrous  connective  tissue.  This 
is  the  periosteum.  It  consists  in  most  instances  of 
an  outer  fibrous  layer,  composed  of  bundles  of  fibrous 
tissue  densely  aggregated,  and  an  inner,  or  osteogenetic 
layer,  which  is  of  loose  texture,  consisting  of  a  mesh- 
work  of  thin  l^undles  of  fibrous  tissue,  in  which 
numerous  hlood-vessels  and  many  protoplasmic  cells 
are  contained.  The  blood-vessels  form  hj  their  capil- 
laries a  network.  The  cells  are  spheroidal  or  oblong, 
each  with  one  spherical  or  oval  nucleus.  They  have 
to  form  bone-substance,  and  are  therefore  called  the 
osteoblasts  (Gegenbaur). 

(b)  Tlie  carlilag-e  is  hyaline  cartilage,  and  its 
distribution  on  and  connection  with  bone  have  been 
mentioned  on  pp.  63  and  64. 

63.  (c)  The  marrow  of  l>oiie  is  a  soft  \'ascular 
tissue,  filling  up  all  spaces  and  cavities.  It  consists 
of  a  very  small  amount  of  fibrous  tissue  as  a  matrix, 
and  in  it  are  embedded  numerous  blood-vessels  and 
cells.  The  few  afierent  arterioles  break  up  into  a 
dense  network  of  capillaries,  and  these  are  continued 
as  plexuses  of  veins,  characterised  by  their  compara- 


Bone.  69 

lively  large  size  and  exceedingly  thin  walls.  The 
cells  are  of  the  same  size,  aspect,  and  shape  as  the 
osteoblasts  of  the  osteogenetic  tissue,  and  they  are 
called  marrow  cells. 

In  origin  and  structure,  the  tissue  of  the  osteo- 
genetic layer  of  tlie  periosteum  and  tlie  marrow  are 
identical.  In  the  embryo,  the  marrow  is  derived 
from  an  ingrowth  of  the  osteogenetic  layer  of  the 
periosteum  {see  below),  and  also  in  the  adult  the  two 
tissues  remain  directly  continuous.  As  will  be  shown 
later,  the  marrow  at  the  growing  ends  of  the  bones 
is  concerned  in  the  new  formation  of  osseous  substance 
in  the  same  way  as  the  osteogenetic  layer  of  the  peri- 
osteum is  in  that  of  the  surface  ;  and  in  both  tissues 
the  highly  vascular  condition  and  the  cells  (osteo- 
blasts of  the  osteogenetic  layer,  and  marrow  cells  of 
the  marrow)  are  the  important  elements  in  this  bone 
formation.  Marrow  is  of  two  kinds,  according  to 
the  condition  of  the  cells.  If  many  or  most  of  these 
are  transformed  into  fat  cells,  it  has  a  yellowish  aspect, 
and  is  called  yellow  marroio  ;  if  few  or  none  of  them 
have  undergone  this  change,  it  looks  red,  and  is  called 
red  marroiD.  In  the  central^  or  marrow,  cavity  of  the 
shaft  of  tubular  bones,  and  in  the  spaces  of  some 
spongy  bones,  the  marrow  is  yellow ;  at  the  ends  of 
the  shaft,  in  the  -spongy  bone  substance  in  general, 
and  in  young  growing  bones  it  is  red. 

Some  of  the  cells,  especially  those  of  red  marrow, 
the  erythrohlasts,  are  the  elements  from  which  nor- 
mally vast  numbers  of  red  blood  corpuscles  are 
formed,  as  has  been  mentioned  on  a  former  page. 

In  marrow,  particularly  in  red  marrow,  we  meet 
with  large  multinucleated  cells,  called  inyeloplaxes  of 
Robin.  They  are  derived  by  overgrowth  from  ordin- 
ary marrow  cells,  and  are  of  importance  both  for 
the  absorption  as  also  for  the  formation  of  bone 
[see  below).      According  to  Heitzmann,  Malassez,  and 


70 


Elements  of  HistoloCjY. 


others,  they  also  have  to  do  witli  the  formation  of 
blood-vessels  and  blood  corpuscles.  NuQierous  eosino- 
phile  cells  are  present  in  the  marrow, 

64.  The  matrix  of  osseous  substance  is  dense 
plexiform  fil^rous  connective  tissue,  i.e.  a  tissue  yield- 
ing- gelatin  on  boiling.  The  cement  substance  between 
the  fibrils  is  petrified,  owing  to  a  deposit  of  insoluble 
inorganic  lime  salts,  chiefly  carbonates  and  phosphates. 
These  can  be  dissolved  out  by  strong  acids  (hydro- 
chloric) and  are  thereby  converted  into  soluble  salts. 
Thus  the  orijanic  matrix  of  osseous  substance — called 
ossein — may  be  obtained  as  a  soft  flexible  material, 
easily  cut. 

In  young  bone  the  matrix  or  ossein  is  a  plexus  of 
trabecuLe  of  fibrous  tissue  (v.  Ebner),  and  in  it  are 
also  a  few  elastic  fibres  to  be  noticed. 

The  bone  substance  is  in  the  adult  state  generally 
lainellated,  the  lamellse  being  of  microscopic  thinness. 
Between  every  two  lamellae  are  numbers  of  isolated, 
flattened,  oblong  spaces — the  hone  lacnnce  (Fig.   49), 

which  anastomose 
by  numerous  fine 
canals  with  one 
another,  and  also 
with  those  of  the 
next  lamella  above 
and  below  (Fig.  50). 
The  appearances  are 
very  similar  to  those 
presented  by  the 
lacunse  and  canali- 
culi  containing  the 
corneal  corpuscles 
as  described  in 
Chapter  V. 

The  bone  lacunte  and  their  canaliculi  are  the 
lymph-canalicular  system  of  osseous  substance,  for  they 


Fig.  49. — Osseous  Lanieihe  ;  oblong  branched 
bone  lacun;e  and  canaliculi  between  them. 
{Atlas.) 


Bone.  7 1 

are  in  open  and  free  communication  with  the  lymphatic 
vessels  of  the  marrow  spaces  and  of  the  Haversian 
canals. 

65.  In  the  bone  matrix,  each  lacuna  contains  also 
a  nucleated  protoplasmic  cell,  called  the  hone  celi, 
which,  however,  does  not  fill  it   completely.     In  the 


Fig.  50. — From  a  Transverse  Section  through  Compact  Bone,  showing 
systems  of  concentric  lamelliB  (with  bone  corpuscles  between)  around 
Haversian  canals.     (From  a  photogram  by  Mr.  Pearce.) 


young  state  the  cell  is  branched,  the  branches  passing 
into  the  canaliculi  of  the  lacunae  ;  but  in  the  old  state 
only  traces  of  the  original  nucleated  cell  and  very  few 
processes  can  be  detected ;  this  with  its  lacuna  and 
canaliculi  is  called  a  bone  corpuscle. 

66.  Accordinsf  to  the  arrano^ement  of  the  bone 
substance,  we  distinguish  compact  from  spongy  sub- 
stance.    The  former  occurs  in   the  shaft  of  tubular 


72  Elemexts  of  Histology. 

bones  and  in  the  outer  layer  of  flat  and  short  bones. 
Its  lamell?e  are  arranged  as :  («)  concentric  or  Haversian 
lamella .,  directly  surrounding  the  Haversian  canals 
(Fig.  51).  These  are  narrow  canals  of  varying  lengths 
pervading   the    compact    substance  in  a  longitudinal 


a 


P'ig.  51.— Compact  Bone  Substance  in  Cross-section.     (Atlas.) 

a.  Concentric  lamellae  arranged  around  the  Haversian  canals,  cut  across;  6,  in- 
termediate or  ground  lamellia  The  bone  lacuna?  are  seen  between  the  bone 
lamellas. 

direction,  and  anastomosing  with  one  another  by 
transverse  or  oblique  branches.  The  Haversian  canals 
near  the  marrow  cavity  are  larger  than  those  near 
the  periosteum.  In  fact,  those  next  to  the  marrow 
cavity  become  gradually  enlarged  by  absorption  of 
the  concentric  lamellse,  until  finally  they  are  fused 
with  the  marrow  cavity.  Each  Haversian  canal  con- 
tains a  blood-vessel,  one  or  two  lymphatics,  and  a 
variable  amount  of  marrow  tissue.  These  canals  open 
both  into  the  marrow  cavity  and  on  the  outer  surface 
into  the  osteogenetic  layer  of  the  periosteum,  and 
they  form  the  means  by  which  the  latter  remains  in 
continuity  with  the  marrow.    Each  canal  is  surrounded 


Bone.  73 

by  a  series  of  concentric  bone  la?7iellcf,  tvith  the  bone 
corpuscles  between  thein,  and  this  is  a  system  of  con- 
centric lanielhe.  Near  the  external  surface  of  the 
compact  substance  the  number  of  lamellae  in  each 
system    is    smaller    than    in    the     deeper    parts,      {b) 


^'^^^mm^g 


Fig.  51a. — Sharjipy's  fibres  amongst  the  iiisterstitial  lamella;  of  a  transverse 
section  of  the  human  humerus  ;  the  fibres  run  in  a  vertical  direction, 
and  surround  spaces  wliicli  contain  the  bone-cells.     {After  KolUker,  I.) 

Between  these  systems  of  concentric  lamellae  are  the 
intermediate  or  ground  lamelhe ;  they  run  in  various 
directions,  and  in  reality  fill  the  interstices  between 
the  systems  of  the  Haversian  or  concentric  lamellae. 
Near  the  external  surface  of  long  bones  they  have  pre- 
eminently a  direction  parallel  to  the  surface.  These  are 
the  circumferential  lamellce  of  Tomes  and  de  Morgan, 
The  ground  lamellae  are  the  earliest  to  be  developed, 
being  the  matrix  of  the  first-formed  spongy  bone, 
and    they   are    the    last    to  disappear  where  bone  is 


74  Elements  of  Histology. 

melted  clown  in  the  marrow  cavity.  The  concentric 
lamellfe,  on  the  other  hand,  are  the  last  to  be  formed 
where  spongy  bone  is  converted  into  compact  bone, 
and  they  are  the  tirst  to  become  absorbed  where  com- 
pact bone  is  reduced  again  to  spongy  bone,  as  near 
the  central  marrow  cavity.  The  lamellae  of  compact 
bone  are  perforated  by  perpendicular  petrified  fibres, 
the  perforating  fibres  of  Sharpey.  They  form  a  con- 
tinuity with  the  fibres  of  the  periosteum,  from  which 
they  are  developed,  through  the  lamellae  of  osseous 
substance  deposited  by  the  osteogenetic  layer  of  the 
periosteum  (Fig.  51a). 

67.  Spongy-  bone  substance  occurs  in  the  end  of 
the  shaft,  in  the  apophyses,  in  short  bones,  and  in  the 
diploe  of  flat  bones.  The  cavities  or  meshes  of  the 
spongy  substance  are  called  Haversian  spaces  or  can- 
celli ;  they  intercommunicate  with  one  another,  and 
are  filled  with  marrow,  which  in  the  vouncf  and  grow- 
inij  state  is  fjenerallv  of  the  red  varietv.  The  firm 
parts  form  spicules  and  septa,  called  hone  trahecuUt, 
of  varying  length  and  thickness,  and  are  composed  of 
lamellae  of  bone  substance. 

According  to  the  arrangement  of  the  trabeculse, 
the  spongy  substance  is  a  uniform  honeycombed  sub- 
stance, or  appears  longitudinally  striated,  as  in  the 
end  of  the  shaft.  In  the  latter  case  the  marrow 
spacas  are  elongated  and  the  trabeculse  more  or  less 
parallel,  but  anastomosing  with  one  another  by 
transverse  Ijranches. 

68.  Development  of  bone.— Bone  is  developed 
in  the  embryo,  and  continues  to  be  fonned  also  after 
birth  as  long  as  bone  grows,  either  in  the  cartilage 
or,  independently  of  this,  directly  from  the  osteo- 
genetic layer  of  the  periosteum.  The  former  mode 
is  called  endodiondral,  or  intracartilagino^is:  the  latter 
periosteal^  or  inter  me mhranous  formation. 

All  the  bones  of  the  limbs  and  of  the  vertebral 


Bone.  7  5 

column,  the  sternum,  and  the  ribs,  and  the  bones 
forming  the  base  of  the  skull,  are  preformed  in  the 
early  em])ryo  as  solid  hyaline  cartilage,  covered  with 
a  membrane  identical  in  structure  and  function  with 
the  periosteum,  which  at  a  later  period  it  represents. 
This  cartilage  is  eventually  replaced  by  bone — 
endochondral  hone.  The  tegmental  bones  of  the 
skull,  the  bones  of  the  face  with  the  lower  jaw, 
except  the  angle,  are  not  preformed  as  cartilage  at 
all.  Only  a  membrane  identical  with  the  future 
periosteum  is  present,  and  underneath  and  from  it 
the  bone  is  gravlually  deposited — i-)eriosteal  hone.  The 
same  deposit  of  periosteal  bone  takes  place  on  all 
bones,  no  matter  what  their  origin,  and  this  deposi- 
tion of  layer  after  layer  of  bone  by  the  osteogenetic 
layer  of  the  periosteum  represents  the  groivtli  of  the 
hone  in  thickness. 

69.  EiKlochoiiclral  foriiiatioii. — The  stage 
next  to  the  one  (1)  in  which  we  have  solid  hyaline 
cartilage  covered  with  periosteum  is  the  following : 
(2)  Starting  from  the  "centre,  or  point,  of  ossifica- 
tion," and  proceeding  in  all  directions,  the  cartilage 
l)ecomes  permeated  by  numbers  of  channels  (cartilage 
channels)  containing  prolongations  (periosteal  pro- 
cesses of  Virchow)  of  the  osteogenetic  layer  of  the 
periosteum — i.e.  vessels  and  osteoblasts,  or  marrow 
cells.  This  is  the  stage  of  the  vascidarisation  of  the 
cartilage.  In  the  next  stage  (3)  the  cartilage  border- 
ing on  these  channels  grows  more  transparent,  the 
lacun{3e  becoming  enlarged  and  the  cartilage  cells 
more  transparent.  The  latter  gradually  break  down, 
while  the  intercellular  trabeculse  become  calcified; 
the  lacume,  by  absorption  of  the  calcified  trabeculfe, 
fusiuff  witli  the  cartilaoje  channels.  These  latter 
thereb}^  become  transformed  into  irregidar  cavities, 
which  are  bordered  by  trahecuhe  of  calcified  cartilage. 
The  cavities  are  the  primary  marroiv  cavities,   and 


76 


Elements  of  Histology. 


they  are  filled  witli  \\\^  jjrimary  or 


j\4  '^'-^-f'^/'i',--,     ^--  ■ 


Fig.  52. — Longitudinal  Section  through  the  entire 
Foetal  Humerus  of  a  Guinea-];)ig. 

fl,  Periosteum  ;  6,  hyaline  cartilage  of  the  epiphysis  ; 

c,  intennediate  cartilage  at  the  end  of  the  shaft ; 

d,  zone  of  calcification  ;  t,  i>eriostealbone,  spongy  ; 
/,  endochondral  bone,  spongy. 


tilage  gradually  assumes  the  appear 


cartilage  marroiv 
— i.e.  blood-ves- 
sels and  osteo- 
blasts, derived, 
as  stated  above, 
from  the  osteo- 
genetic  layer  of 
the  periosteum. 
(4)  The  osteo- 
blasts arrange 
themselves  by 
active  multipli- 
cation in  a  special 
layer  on  the  sur- 
face of  the  calci- 
fied cartilajje 
trabeculse  pro- 
jecting into  and 
bordering  the 
primary  marrow 
cavities.  The 

osteoblasts  form 
hone  substance — 
osseous  matrix 
and  branclied 
bone  corpuscles 
— and  as  this 
proceeds,  the  cal- 
cified cartilage 
trabecules  become 
gradually  en- 
sheathed  and 
covered  icitli  a 
layer  of  osseous 
substance.  Thus 
the  original  car- 
ance  of  a  spongy 


Bone.  7  7 

substance,  in  wliicli  the  cavities  (primary  marrow 
cavities)  arc  tilled  with  the  primary  marrow,  and 
are  of  considerable  size,  while  the  trabecuhe  bor- 
dering them  are  calcified  cartilage  covered  with 
layers  of  new  bone.  The  marrow  cells,  or  osteo- 
blasts, continue  to  deposit  bone  substance  on  tlie 
free  surface  of  the  trabecul?e,  while  the  calcified 
cartilage  in  the  centre  of  the  trabeculte  gradually 
becomes  absorbed. 

70.  The  nearer  to  the  centre  of  ossification,  the 
more  advanced  is  the  process — i.e.  the  more  bone  and 
the  less  calcified  cartilage  is  found  constituting  the 
trabecuhe,  and  the  thicker  the  latter.  At  the  "  centre 
of  ossification,"  i.e.  whence  it  started,  the  process  is 
farthest  advanced  ;  away  from  it,  it  is  in  an  earlier 
stage.  At  this  period  of  embryo  life,  between  the 
centre  of  ossification  and  a  point  nearer  to  the  ex- 
tremity of  the  shaft  of  a  long  bone,  all  stages  described 
above  may  be  met  with — viz.  between  the  solid 
unaltered  hyaline  cartilage  at  the  end  of  the  shaft 
and  the  spongy  bone  with  the  unabsorbed  remains  of 
calcified  cartilage  in  the  middle  of  the  shaft  all 
intermediate  stages  occur  (Fig.  52). 

71.  After  birth,  and  as  long  as  bone  grows,  we 
find  in  the  end  of  the  shaft,  and  also  in  the  epiphysis, 
a  continuation  of  the  process  of  endochondral  forma- 
tion described  above.  In  fact,  all  bones  preformed 
in  the  embryo  as  cartilage  grom)  in  length  before  and 
after  birth  by  endochondral  formation  of  new  bone. 
The  hyaline  cartilages  at  their  extremities,  the  carti- 
lage of  the  epiphysis,  the  intermediate  cartilai^e  at 
the  end  of  the  shaft,  are  the  cartilages  at  the  expense 
of  which  the  new  bone  of  the  epiphysis  and  of  the 
end  of  the  shaft  respectively  are  formed  by  the  marrow 
(blood-vessels  and  marrow  cells  or  osteoblasts)  in 
contact  with  the  cartilage.  As  long  as  this  cartilage 
continues  to  grow,  so  long  is  there  new  formation  of 


78 


Elemexts  of  Histology. 


bone  by  the  marrow  encroaching  on  it,  or,  in  other 
words,  so  long  is  there  growth  in  length  of  the  shaft. 
When  at  a  certain  period  of  adidt  life  the  growth 
of  the  intermediate  cartilage  has  come  to  an  end,  the 
cartilage  is  completely  replaced  by  the  spongy  bone 


y^^M 


m:\\b    «      i   (f^,^m      rt^  Q)%    /fiT 


■*   \i*  it) 


'W 


Fig.  53. — From  a  Transverse  Section  tlirough  the  Tibia  of  Foetal  Kitten. 

a.  Fibrous  layer  of  the  periosteum;  b,  osteogenetic  Inyer  of  the  periosteum; 
c.  periosteal  bone;  d,  calcifled  cartilage  not  covered  yet  by  bone;  below  this 
layer  the  tralieculte  of  calcified  cartilage  covered  with  plates  of  bone — 
sbaded  darkly  in  the  figure  ;  e,  boundary  between  periosteal  and  endochondral 
bone.    iAtlas.) 


Bone. 


79 


of  the  end  of  the  shaft,  and   this  is  not  capable  of 
further  lengthening. 

72.  Following  the  development  of  a  tubular  bone 
after  the  above  mentioned  stage  4,  we  find  that  the 
spongy  bone  once  formed  is  not  a  permanent  structure, 


Fig.  54.— From  a  Section  through  the  Intermediate  Cartilage  of  Femur  of  a 
Foetus.  Low  magnifjing  power.  {From  a  photogrcqjh  by  Mr.  A. 
Pringle.) 

a,  intermediate  cartilajsre  ;  b,  cartilage  of  the  eiiiiihysis ;  c,  spongy  bone  of 
epiphysFs ;  d,  spongy  bi>ne  at  the  end  of  the  shaft. 

but  becomes  gradually  absorbed  altogether,  and  this 
process  also  starts  from  the  points  of  ossification. 
Thus  a  f;rc\dual  enlargement  and  ultimate  fusion  of 
the  marrow  cavities  of  the  spongy  endochondral  bone 


8o  Elements  of  Histology. 

into  one  continuous  cavity  takes  place.  This  repre- 
sents the  rudiment  of  the  future  central  marrow 
cavity  of  the  shaft.  Simultaneously  with,  or  some- 
what previous  to,  this  absorption  of  the  endochondral 
bone,  new  bone  of  the  nature  of  spongy  hone  is 
deposited  directly  hy  tlie  osteogenetic  layer  of  the 
periosteum  on  the  outer  surface  of  the  endochondral 
hone.  This  also  commences  at  the  centre  of  ossifica- 
tion, and  proceeds  from  here  gradually  to  further 
l^oints.  This  is  the  tirst  rudiment  of  the  periosteal 
hone  of  the  shaft  (Figs.  52,  53).  It  is  formed  without 
the  intervention  of  cartilage  directly  by  the  osteo- 
blasts of  the  osteogenetic  layer.  And  as  fresh  masses 
of  osteoblasts  become  developed  l)y  division,  new 
layers  of  spongy  bone  are  formed  by  the  change  of 
the  former  into  bone  matrix  and  bone  cells,  and  the 
old  trabecular  become  increased  in  thickness.  In  the 
meshes  or  Haversian  spaces  of  this  new  spongy 
periosteal  bone  the  same  tissue  is  to  be  found  that 
constitutes  the  osteogenetic  layer  of  the  periosteum, 
the  one  being  derived  from,  and  continuous  with,  the 
other. 

In  these  Haversian  spaces  concentric  lamellai  of 
bone  substance  become  subsequently  formed  by  the 
osteoblasts,  while  at  the  same  time  the  Haversian 
spaces,  being  narrowed  in  by  the  deposit  of  the  con- 
centric lamellae,  are  transformed  into  the  Haversian 
canals.  The  original  spongy  bone  represents,  there- 
fore, the  ground  substance  (primary,  or  ground  lamella?), 
in  which,  or  rather  in  the  spaces  of  which,  the  secondary 
deposit  of  the  concentric  lamella}  or  Haversian 
systems  of  bone  lamellae  takes  place,  by  which  deposit 
the  spongy  bone  becomes  transformed  into  compact 
bone.  This  process  is  farthest  advanced  in  the 
middle  of  the  thickness  of  the  shaft,  and  least  near 
the  periosteum.  When  this  compact  bone  is  again 
absorbed — e.g.  that  next  the  medullary  cavity  of  the 


Bone. 


8r 


sliaft  of  a  long  bone— tlie  concentric  lamella?  are  first 
absorbed,   the    Ha- 


be- 
way 
and 


versian    canal 
ing     in     this 
widened     out 
again    transformed 
into     a    Haversian 
space. 

While,  then, 
the  bone  first  de- 
posited by  the  peri- 
osteum is  of  a 
spongy  character, 
and  gradually  be- 
comes transformed 
into  comi3act_,  the 
reverse  is  ""oing  on 
at  the  same  time 
near  the  marrow 
cavity,  inasmuch 
as  compact  bone  is 
here  changed  into 
spongy  bone,  and 
this  ultimately  dis- 
a23pears  and  be- 
comes absorbed  by 
the  mari'ow. 

73.  At  birth 
all  the  primary  en- 
dochondral bone  «. 
has  already  disap- 
peared by  absorp- 
tion from  the  centre 
of  the  shaft,  and 
the  bone  present  is 
all  of  periosteal  origin 
shaft 


Fig.  55. — From  a  Longitudinal  Section 
Femur  of  Rabbit,  through  the  part  in 
which  the  intermediate  cartiLige  joins 
the  end  of  the  shaft.     {Atlas.) 

a,  Intermediate  cartilage;  6,  zone  of  calcified 
cartilage  ;  c,  zone  in  which  the  calcified  tra- 
heculEB  of  cartilage  become  gradiiRlly  in- 
vested in  osseous  substance,  shaded  light  in 
the  figure;  the  spaces  between  the  tral>e- 
cula3  contain  marrow,  and  the  cai>illar.v 
blood-vessels  are  seen  here  to  end  in  loops  ; 
d,  in  this  zone  there  is  more  bone  formed; 
the  greater  amount  the  farther  away  from 
this  zone. 


At   the  extremity  of  the 
however,  tlie  spongy  bone  is  all  endochondral 

G 


82  Elements  of  Histology. 

bone,  and  it  continues  to  grow  into  the  interme- 
diate cartilage  as  stated  above,  so  long  as  the 
bone  grows  as  a  whole  (Fig.  55).  Of  course  the 
parts    of    this    spongy    bone    nearest    to    the    centre 


'^' 


\% 


^^§)^ 


Fig.  5(3. — Small  mass  of  Boiie  Substance  in  the  Periosteum  of  the  Lower 
Jaw  of  a  Human  Foetus.     [Atlas.) 

tt, Osteou'enetic  liiyer  of  periosteum  ;  l>.  luuliiuiicle.ired giuiit  cells,  inyeloiil.ixes. 
Tbe  one  in  the  midcile  of  the  upper  margin  is  an  osteoclast,  whereas  the 
smaller  one  at  the  left  upper  corner  appears  concerned  in  the  fornntion  of 
bone.  Above  c  the  osteoiihist  cells  become  surrounded  by  osseous  substance 
and  thus  become  converted  into  bone  cells. 

of  the  shaft  are  the  oldest,  and  ultimately  dis- 
appear by  absorption  into  the  central  medullary 
cavity.  In  the  epiphysis  the  spongy  bone  is  also 
endochondral  bone,  and  its  formation  is  connected 
with  the  deep  layer  of  the  articular  cartilage,  but 
more  so  with  the  hyaline  cartilage  separating  the 
epiphysial  spongy  bone  from  the  intermediate  carti- 
lao-e  (see  c  of  Fisj.  oi). 

Underneath  the  periosteum  and  on  the  surface  of 
the  spongy  endochondral  bone  at  the  extremity  of  the 
shaft,   the  periosteal   bone  is  represented  only  by  a 


Bone. 


83 


thill  liiyer,  extending  as  far  as  the  periosteum  reaches 
— e.g.  to  tlie  margin  of  the  articular  cartilage. 

74.   liiteriuoiiibrsiiioiis  format  ion. — All 


Fig.  57.— From  a  Longitudinal  Section  through  the  Spongy  Bone  of  Shaft, 

near  the  intermediaiy  cartilage,  of  Foetal  Kitten,  showing  the  formation 

of  osseous  substance  on  tlie  calcilied  cartilage.     {Atlas.) 

a,  Mhitow  space,  with  bluud-vcssei ;  6,  caicifled  cartilage,  covered  with  isolated 

or  confluent  zoues  of  new  osseous  substance,  consisting  of  fibrillated  bone 

matrix,  bone  lacuna,  and  in  it  a  bone  cell. 


84 


Elements  of  Hjstologv. 


Fig.  58. — From  a  Lolly  itudiual  Section 
of  Femur  of  Rabbit,  close  to  the 
intermecliate  cartilage. 

a,  Calcified  cartilage,  next  to  the  inter- 
mediate cartilage;  6, calcified  carti- 
lage covered  with  thin  layer  of 
bone  ;  c,  uiari'ow  spaces  containing 
osteoblasts,  forming  bone  on  the 
calcified  cartilage;  d,  niyeloplaxes 
(chondroclastsj. 


bones  not  preformed  in 
the  embryo  as  cartilage 
are  developed  directly 
from  the  osteogenetic 
layer  of  the  periostemii  in 
the  manner  of  the  i^eri- 
osteal  bone  described  on 
p.  80.  Here  also  the  new 
l)one  is  at  first  spongy 
bone,  which  in  its  deeper 
or  older  layers  gradually 
becomes  converted  into 
compact  bone. 

In  all  instances  dm'ing 
embryonic  life  and  after 
birth  the  growth  of  a 
bone  in  thickness  takes 
place  after  the  manner  of 
periosteal  or  intermem- 
hranous  hone ;  this  is  at 
first  spongy,  but  is  gra- 
dually converted  into 
compact  bone. 

75.  All  osseous  sub- 
stance is  formed  in  the 
embryo  and  after  bii  th  by 
the  osteoblasts,  or  marrow 
cells  (Gegenbaur,  Wal- 
deyer)  :  each  osteoblast 
oivino:  orioin  to  a  zone 
of  osseous  matrix,  and  re- 
maininof  in  the  centre  of 
this  as  a  nucleated  ^yo- 
toplasmic  remnant,  which 
gradually  becomes 
branched  and  transformed 
into    a   bone    cell.      The 


Bone.  85 

osseous  matrix  is  at  first  a  soft  fil)nllar  tissue,  but  is 
gradually  and  uuiformh^  impregnated  with  lime  salts. 
This  impregnation  always  starts  from  the  centre  of 
ossification  (Fig.  57). 

76.  Wherever  in  the  embryo  or  adult,  in  health 
or  disease,  absorption  of  calcified  cartilage  or  of  osseous 
substance  is  going  on,  we  meet  witli  the  multi- 
nucleated large  protoplasmic  cells  called  the  myelo- 
plaxes  of  Robin.  K()lliker  showed  them  to  be  import- 
ant for  the  absorption  of  bone  matrix,  and  called 
them  therefore  osteoclasts  (Fig.  5Q).  For  cartilage  they 
ma}"  be  called  chondroclasts  ( Fig.  58).  When  concerned 
in  the  absorption  we  find  these  myeloplaxes  situated 
in  smaller  or  larger  pits,  which  seem  to  have  been 
produced  by  them;  these  absorption  pits  or  lacunae  on 
the  surface  of  l)ones  are  called  Howships  lacunce. 
They  invariably  contain  numbers  of  osteoclasts.  It 
can,  however,  be  shown  that  myeloplaxes  are  also 
concerned  in  the  formation  of  bone  by  giving  origin 
to  a  number  of  new  osseous  zones  with  their  bone 
cells.  In  the  earliest  stages  of  development  of  the 
ftetal  jaw"  this  process  is  seen  with  great  distinctness 
(Fig.  56). 

77.  Dentine  forms  the  chief  part  of  a  tooth.  It 
consists  of  a  petrified  matrix  in  which  are  numbers  of 
perpendicularly  arranged  canals — the  dentinal  tubes — 
containing  the  dentinal  fibres.  It  is  in  some  respects 
similar  to  bone,  although  diftering  from  it  in  certain 
essentials.  It  is  similar  inasmuch  as  it  is  developed 
in  like  manner  by  some  peculiarly  transformed 
embryonic  connective  tissue — viz.  by  the  tissue  of  the 
embryonic  tooth  papilla — and  inasmuch  as  cells  are 
concerned  in  the  production  both  of  the  petrified 
matrix  (impregnated  with  lime  salts)  and  of  the 
processes  of  the  cells  contained  in  its  canals — the 
dentinal  fibres.  The  details  of  structure  and  distri- 
bution will  be  described  in  connection  with  the  teeth. 


86 


CHAPTER    V]II. 

XOX-STRIPED    MUSCULAR    TISSUE. 

78.  This  tissue  consists  of  nucleated  cells,  which, 
unlike  amoeboid  cells,  are  contractile  in  one  definite 
direction,  becoming'  shorter  and  thicker  diirinc;  con- 
traction. 

The  cells  are  elongated^  spindle-shaped,  or  band-like 
(Fig.  59),  and  drawn  out  at  eacli  extremity  into  a 
lonuer   or  shorter,   sfenerallv   single,  but  occasionally 


Fig.  59.— Xon-striped  Muscular  Fibres,  isolated.     (Atlas.) 

The  cross-markings  indicate  corrugations  of  the  elastic  sheath  of  the  individual 

fibres. 

branched,  tapering  process.  Each  cell  includes  an 
oval  nucUAis,  which  is  flattened  if  the  cell  it  belongs 
to  is  flattened.  The  cell  substance  is  a  pale,  homo- 
geneous-looking or  longitudinally  striated  substance. 

During  extreme  contraction  the  nucleus  may  be- 
come more  or  less  plicated,  so  that  its  outline  becomes 
wavv  or  zicj-zag. 

It  lias  been  shown  by  Klein  in  certain  preparations 


Non-striped  Muscular   Tjssue.  87 

— e.y.  the  non-striped  muscle  cells  of  the  mesentery  of 
tlie  newt — that  each  muscle  cell  consists  of  a  delicate 
elastic  shentJi,  inside  of  which  is  a  bundle  of  minute 
fibrils  which  cause  the  longitudinal  striation  of  the  cell. 
These  fibrils  are  the  contractile  portion  ;  and  they  are 
contractile  towards  the  nucleus,  with  whose  intra- 
nuclear reticulum  they  are  intimately  connected. 
AVhen  the  cell  is  contracted  its  sheath  becomes  trans- 
versely corrugated  (Fig.  GO). 

79.  The  non-striped  muscular  cells  are  aggregated 
into  smaller  or  larger  bundh>^  by  an  interstitial  alV)U- 


Fig.  60.— Xon-stiipL'<l  Muscular  Cell  of  Mesenteiy  of  Xewt.     {Atlo.s.) 

Sliowin:,'  several  places  whei'e  the   muscular  substance  appears  cuntracted, 
thickened.    At  these  places  the  corrugations  of  the  sheath  are  mariced. 

minous  homogeneous  cement  substance,  the  cells  being 
imbricated  with  their  extremities.  The  bundles  may 
form  a  plexus,  or  they  may  be  aggregated  by  fibrous 
connective  tissue  into  larger  or  smaller  groups,  and 
these  again  into  continuous  masses  or  membranes.  In 
the  muscular  coat  of  the  bladder  of  the  frog,  in  the 
choroidal  portion  of  the  ciliary  muscle,  in  the  arrector 
pili,  in  the  muscular  tissue  of  the  scrotum,  very  well 
marked  plexuses  of  bundles  of  non-striped  muscular 
cells  may  l)e  met  with.  In  the  muscularis  mucosae  of  the 
stomach  and  intestines,  in  the  outer  muscular  coat  of 
the  same  organs,  in  the  uterus,  bladder,  etc.,  occur 
continuous  membranes  of  non-stri})ed  muscular  tissue. 

When  the  muscular  cells  form  larger  bundles  they 
are  more  or  less  pressed  against  one  another,  and 
therefore  in  a  cross-section  appear  of  a  polvgonal 
outline. 

80.   Non-striped  muscular  tissue  is  found  in  the 


88  Elements  of  Histology. 

following  places  :    In  the  muscularis  mucosae  of  the 

oesophagus,  stomach,  small  and  large  intestine  ;  in  the 

outer  muscular  coat  of  the  lower  two-thirds  or  half 

of  the  human  oesophagus  ;  in  that  of  the  stomach,  small 

and  large  intestine ;    in  the  tissue  of  the  pelvis  and 

outer  capsule  of  the  kidney  ;  in  the  muscular  coat  of 

the  ureter,  bladder,  and  urethra  ; 

a  *^  in  the  tubules  of  the  epididymis, 

f%^*^-^        in    the    vas    deferens,    vesiculfe 

^      ^  .,        ^  ^  >eminalis    and    j^rostate ;   in    the 

^.    ,     ,   9    ^  -  corj^ora  cavernosa  and  spongiosa ; 

■"''"     '  '     .^    ,  _  ill  the  tissue  of  the  ovary  and  in 

'      .   .       the  broad  ligament :  in  the  mus- 

x^  -^  cular    coat    of    the   oviduct,    the 

uterus  and   vagina ;    in   the  pos- 

Fig.61.-From  a  Transverse     terior    part    of    the    Wall     of     the 
Section  through  Bundles     \y^r.\^r.^  .      infhp    Inrcrp  and  cimnll 

of  Non-striped  Muscular    ^racnea  ,     mine  large  ana  small 

Tissue  of  the  Intestine,      bronchi,    in    the    alveolar    ducts 

'^%^l^l^Jt'.  c'uT^,    and  infundibula  of  the  lung  ;  in 

cor^cie"^of%=he'flga?l    the    pleura   pulmonalis   (guinea- 

?{:^''irinre.^'^ril!e''et    pig) ;  in   the    peritoneum  of  the 

ceii"""(4itol)"'^  """'"^^    frog  and  newt,  in  the  upper  part 

of  the  upper  eyelid,  and   in  the 

fissura     orbitalis ;      in     the     sphincter     and     dilator 

pupilliTe,    and    the     ciliary     muscle ;     in    the    capsule 

and  trabecular   of   the   spleen,    and  the   trabecular  of 

some    of    the    lymphatic    glands  ;   in    the    arrectores 

pilorum,    and  sweat  glands  of  the  skin,    the    tunica 

dartos  of  the  scrotum  ;  in  the  tissue  of  the  nipple  of 

the   breast  ;    in  the  larcfe  ducts  of  the  sali^'arv   and 

pancreatic  glands  ;    and  in  the  muscular  coat  of  the 

gall  bladder,  the  hepatic  and  cystic  duct.      The  aorta 

and  the  arteries  have  a  large  amount  of  non-striped 

muscular  tissue,  the  veins  and  lymphatics  less. 

81.  As  regards  length,  the  muscular  cells  vary 
within  considerable  limits  (from  ^\-^  to  0-5  millimeter), 
those  of  the  intestine,  stomach,  respiratory,  urinary. 


NoN-STKiPED  Muscular  Tissu/-:.  89 

and  genital  organs  being  very  long  as  compared  with 
those  of  the  blood-vessels,  which  are  sometimes  only 
twice  or  thrice  as  long  as  they  are  broad,  and  at  tlie 
same  time  branched  at  their  extremities. 

Non-striped  muscular  tissue  is  richly  supplied  with 
blood-vessels,  the  capillaries  forming  oblong  meshes, 
though  their  number  is  not  so  great  as  in  striped 
muscle.  The  nerves  of  non-striped  muscle  are  all 
derived  from  the  sympathetic  ;  their  distribution  and 
termination  will  be  described  in  a  future  chapter 


90 


CHAPTER  IX. 

STRIPED    MUSCULAR    TISSUE. 


82.   The  striped  muscular   tissue  is  composed  of 
long  cylindrical  fibres,  some  measuring  in  length  as 


Fig.  02.— Striped  Muscular  Fibres  of  the  Tongue  of  a  Guinea-pig,  of  which 
the  blood-vessels  have  been  injected  with  carmine  gelatine.  Owing  to 
the  contracted  state  of  the  niuscular  tibres  the  capillaries  are  much 
twisted  and  wavy  ;  in  several  places  tlie  "  safety  receptacles  "  are  well 
show  n.     (From  a  microplwto. ,  moderatehi  magnified.) 

mucli  as  1.^-2  inches,  others  are  much  shorter;  their 
thickness  varies  between  ^-^o  ^^  e^o  ^^  ^^^  inch.     The 


Striped  Muscular   Tissue.  91 

til:) res  are  regularly  transversely  striated,  and  are 
therefore  called  the  striped  oi'  striated  muscular  fil)res 
By  fibrous  connective  tissue  they  are  grouped  together 
so  as  to  form  larijer  or  smaller  bundles — muscular 
fasciculi  ;  the  connective  tissue  surrounding  the 
bundles  is  called  the  perimT/sium  ;  while  the  delicate 
connective  tissue  passing  from  the  perimysium  into 
the  bundle,  and  separating  the  individual  muscular 
fibres  from  one  another,  is  called  the  endomysium. 
The  perimysium  is  the  carrier  of  the  larger  vascular 
and  nervous  branches,  while  the  endomysium  contains 
the  capillaries  and  the  terminal  nerves.  The  capil- 
laries form  very  rich  networks  with  elongated  meshes, 
and  are  always  situated  between  the  individual 
muscle  fibres.  The  capillaries  and  veins  appear  very 
wav^y  and  twisted  in  the  contracted  bundles,  and 
straighter  in  the  uncontracted  bundles  (Fig.  62).  The 
small  vessels  are  provided  here  and  there  with  j)eculiar 
saccular  dilatations,  which  act  as  a  sort  of  safety 
receptacle  for  the  blood  when,  during  a  sudden 
intense  contraction,  it  is  pressed  out  from  some  of 
the  capillaries. 

83.  Each  muscular  fibre  during  contraction  be- 
comes shorter  and  thicker.  In  the  living  uninjured 
muscular  tibres,  sjDontaneously  or  after  the  application 
of  a  stimulus,  a  contraction  starts  at  one  point  and 
passes  over  the  whole  muscular  fibre  like  a  wave — 
contraction  vxive — the  progress  of  which  is  noticeable 
by  the  thickening  rapidly  shifting  along  the  fibre,  the 
part  behind  resuming  its  previous  diameter. 

84.  A  striped  muscular  fibre  consists  of  (1)  a 
delicate  hyaline  elastic  sheath,  the  sarcolenima,  and 
(2)  the  rnuscniar  contents.  It  is  the  structure  of  the 
latter  which  has  given  origin  to  a  variety  of  theories, 
owing  to  optical  difficulties  in  examining  fresh  and 
living  fibres,  and  owing  to  the  varied  changes  it  is 
liable  to  undergo  when  acted  upon  by  many  reagents. 


92 


Elemexts  of  Histology. 


jMJS8S»i»i*9f^^§i^f/ 


;i^6siJ^aS 


1;     . 

»S24? ji ;t5J 

t  "  vC^S 

In  the  following  we  shall  adopt  the  view  enunciated 
by  Rollett  during  recent  years  ;  we  think  that  his 
conclusions  are  based  on  extensive  observations  and 
study  of  muscular  fibres  in  vertebrates  and  inverte- 
brates under  the  best  conditions,  and  his  conclusions 
harmonise  best  with  the  classical  observations  of 
Bowman,    Briicke,   Cohnheira,   and    Engelmann,    and 

with  observations  which  can 
g  ---.,„.,,,,.,,.,,,  3  be  verified  by  careful  study 
f  of  fresh  muscular  fibres. 

S5.  The  contents  of  a  mus- 
cular fibre  consist  of  two  prin- 
cipal parts  (Figs.  63,  G4) :  {a) 
the  fihrillce,  or  rhabdia  of 
Kiihne ;  and  (h)  the  sarco- 
plas'/ii  or  intertibrillar  sub- 
stance, a  hyaline  or  faintly 
granular  substance,  having 
resemblances  to  protoplasm, 
and  acting  as  the  matrix  for 
the  tibrilhe.  The  fibrillar  ex- 
tend in  a  longitudinal  direc- 
tion  parallel  to  the  long  axis 
of  the  muscular  fibre,  and  they 
are  grouped  together  into 
bands,  strands,  or  tubes,  called 
the  muscle  columns ;  the  latter 
larger  groups.  The  sarco- 
plasm  fills  up  all  interstices  between  the  groups  of 
the  muscle  columns,  between  the  columns  of  each 
group,  and  between  the  fibrillfe  of  each  column.  The 
amount  of  sarcoplasm  between  the  groups  of  columns 
is  generally  greater  than  between  the  columns  of  each 
group.  During  growth  and  regeneration  of  mus- 
cular fibres  in  the  adult  the  collections  of  nucleated 
sarcoplasm  on  the  surface  —i.e.  underneath  the  sarco- 
lemma — become  conspicuously  increased  in  vertebrate 


Fig.  63. — Part  of  a  Muscular 
Fibre  of  Geotruxjes  sylva- 
ticus,  showing  its  compo- 
sition of  fibrillit.  {Rollett.) 

I,  Intermediate  disc  (Krause's 
membrane) ;  s,  sarcous  ele- 
ments. 


are     aorgresfated 


into 


Striped  Muscular   Tissue. 


93 


muscular  tibres,  both  in  number  and  size  ;  and  they  are 

the  material  from  which  muscular  fil^rilhe  are  formed. 

Special   collections  of  nucleated 

sarcoplasm    are     found    at    the 

termination  of  the  motor  nerve 

tiljre  in  the  muscular  fibre  [see 

below). 

On  observing  a  cross  section 
through  fresh  or  well-preserved 
muscular  fibres,  the  sarcoplasm 
is  seen  as  transparent  lines  sub- 
dividing the  muscular  contents, 
which  appear  dim  like  ground 
glass,  into  small  more  or  less 
polyhedral  areas,  the  areas  of 
Cohnheim.  These  areas  are  the 
cross-sections  of  the  muscular 
columns,  and  are  therefore  made 
up  of  a  number  of  granules, 
the  optical  cross-sections  of  the 
constituent  fibrillae.  The  mus- 
cular columns  appear  aggre- 
gated by  larger  accumulations 
of  sarcoplasm  into  larger  or 
smaller  groups ;  and  between 
the  groups  the  sarcoplasm  is 
again  greater  than  between  the 
fibrillae  of  each  column,  and  in 
this  respect  there  exists  the 
greatest  variety  between  the 
different  animals.  In  the  per- 
fectly fresh  condition  tlie 
amount  of  sarcoplasm  between 
the  fibrilhe  of  a  column  is 
in  some  cases  insignificant, 
and    almost    appears    absent    from     place     to    place. 

Tlie   sarco[)lasm    shows    also    other   differences  of 


A'— 


\ 


jL 


Fig.  64. — Mu>;cul;ir  Fibre, 
stained  with  hitmatoxy- 
lin,  of  Staphylinuscaesa- 
reus.     {liollett.) 

I,  Interniefliate  disc  (Krause's 
membrane  or  Dobie's 
layer);  L,  secondarj'  disc 
(placed  witliiii  tlie  lateral 
disc  ur  Floi-'el's  layer) ; 
T,  tranverss  disc  (sarcoiis 
eleiiieats);  x,  nucleus  of 
muscle  corpuscle. 


Q4  Elements  of  Histology. 

distribution  ;  in  the  muscular  libres  of  many  insects 
it  generally  forms  a  cylindrical  accumulation  in  the 
centre  of  the  muscular  fibres,  containing  spherical 
nuclei  ;  from  it  thinner  septa  pass  between  the  groups 
of  muscular  columns.  In  vertebrate  muscular  fibres 
the  sarcoplasm  forms  small  plate-like  or  angular  col- 
lections on  the  surface  of  the  muscular  contents — i.e. 
immediately  under  the  sarcolemma.  These  collections 
include  spherical,  or  more  generally  oval,  nuclei,  and 
are  called  the  muscle  corpuscles.  The  whole  sarco- 
plasm must  be  considered  as  a  sort  of  protoplasmic 
basis,  and  the  muscle  corpuscles  as  the  nucleated  accu- 
mulations of  it. 

86.  Each  hbrilla  shows  along  the  whole  length  of 
the  muscular  fibre  regular  alterations,  as  regards  both 
aspect  and  thickness  of  its  sul)stance,  and  accordingly 
can  be  considered  as  consisting  of  different  portions 
following  each  other  endwise,  and  repeating  them- 
selves uniformly  and  in  regular  manner  throughout 
the  whole  length  and  thickness  of  the  muscular  fibre. 
These  portions  are  the  sarcous  elements  of  Bowman, 
dim,  homogeneous  rods  or  prisms  forming  the  chief 
parts  ;  between  each  tw^o  successive  sarcous  elements 
of  the  saQie  fibrilla,  at  equal  distance,  is  a  dark  granule, 
sometimes  double,  to  whicli  the  end  of  each  sarcous 
element  is  joined  by  a  thin  bridge.  In  the  fresh  state 
the  sarcous  elements  are  prisms,  and  those  of  con- 
tiguous fibrilla?,  almost  touch  each  other  at  their  sides, 
so  that  little  or  no  sarcoplasm  intervenes  between 
them  here ;  but  when  the  sarcous  elements  shrink 
— e.g.  after  death  or  after  hardening  reagents,  or 
sometimes  even  duriiig  life  and  during  contraction — 
they  are  more  or  less  hourglass-shaped,  and  are 
separated  by  thin  layers  of  sarcophism  from  those 
of  contiguous  fibrillse.  The  bridge  by  which  each  end 
of  a  sarcous  element  is  joined  to  the  granule  being 
much    thinner  than  the  latter,   there   is  more  sarco- 


Sir  IP /CD  Muscular   Tissue. 


95 


granules  of  the 


plasm  present  in  the  layer  containing  the  bridge; 
and  since  the  sarcoplasm  is  more  transparent  than 
either  the  sarcous  elements  or  the 
fibrilla^  the 
nmscnlar  libre 
as  a  whole 
shows  a  con- 
s  p  i  c  u  o  u  s 
transparent 
layer  or  disc 
between  each 
layer  of  the 
dark  granules 
and  each  layer 
of  the  sarcous 
elements.  This 
causes  the 
transverse 
striation.  The 
layer  of  the 
dark  granules 
corresponds  to 
tlie  line  of 
Dohie,  or  the 
line  of  Amici, 
or  the  inter- 
mediate disc  of 

Engelmann,  or  the  yneinhrane  of  Krause.  The 
layer  or  disc  of  sarcoplasm  in  which  the  bridges 
are  placed,  which  join  the  sarcous  elements  to 
the  granules  of  the  intermediate  disc,  is  the  lateral 
disc.  The  layer  or  disc  of  sarcous  elements  corre- 
sponds to  the  transverse  disc.  In  many  muscular 
fibres  of  insects,  notably  in  those  of  the  crab  (Ruther- 
ford), there  occurs  in  each  fibrilla  witliin  the  lateral 
disc  a  short  rod-like  thickening  midway  between  the 
sarcous  element  and  the  dark  granule  ;   the  layer  or 


E 


Fis. 


05.— Striped    Muscular  Fibres   of   the   Water 
Beetle  (Hydropliilns).     {Atlas.) 

Sarcoleiuraa;  b,  Krause's  menibrane.  The  sarcous 
eliiiient^;  are  well  seen.  In  a  the  oblong  nuclei  of 
tlie  muscle  corpuscles  nre  shown.  In  b  the  sarco- 
lennua  has  become  unnaturally  raised  from  the  mus- 
cular contents.  The  contractile  discs  are  M^ell 
shown  :  so  also  are  the  sarcons  elements. 


96 


Elements  of  Histology. 


y^-\ 


disc  of  these  rods  or  grannies  forms 
the  secondary  disc,  or  the  Layer  of 
Flcigel. 

cS7.  A  typical  niuscnlar  fibre  shows 
then,  owing  to  the  differentiation  of 
each  fibrilla  into  the  above  portions, 
the  following  layers  in  regular 
alternation  throughout  the  thickness 
of  the  fibre :  (1)  27ie  dark  inter- 
mediate disc,  Dobies  line,  or  Kraiise's 
membrane ;  (2)  the  transparent 
lateral  disc  ;  (3)  the  dim  transverse 
disc  of  sarcous  elements.  Then  fol- 
lows another  transparent  lateral  disc, 
and  then  again  the  intermediate 
disc. 

As  stated  above,  in  some  fibres 
the  line  of  Dobie  is  a  double  row 
of  granules,  and  the  transparent 
lateral  disc  contains  a  line  of  granules, 
Flugel's  layer. 

The  intermediate  disc  appears  to 
be  intimately  connected  with  the 
sarcolemma ;  hence  Krause  gave  it 
the  name  of  a  membrane.  When  a 
muscular  fibre  contracts  during  life, 
or  when  it  shrinks  after  death,  the 
sarcolemma  shows  regular  bulgings 
between  each  two  Krause's  mem- 
branes ;   at    these    latter    the    sarco- 


Fig.  66. — Three  Fibrilke  of  Crab's  Muscle,  showing 
the  successive  stages  from  complete  relaxation 
(?•)  to  complete  contraction  (t).  (From  Rtither- 
foi'd's  "  .'itructui-e  and  Contraction  of  Striped 
Muscular  Fibre.") 

b — 610,  The  various  appearances  of  the  sarcous  ele- 
ments; d—(l9,  the  appearances  of  Dol>ie's  granules  ; 
/,  Flogel's  granules ;  c,  clear  layer  (lateral  disc) 
between  Flogel's  granules  and  end  of  sarcous 
elements. 


STK/r/lD    Ml'SCULAR     TiSSi'E. 


97 


lemma  is  drawn  in.  The  part  of  a  muscular  fihn; 
between  two  neighbouring  Krause's  membranes  and 
the     corresponding    portion    of    the    sarcolemma    is 


Fij;-.  t)7. — Semi-schematic  representation  of  portions  of  Fibrils  of  Crab's 
Muscle,  showing  the  appearances  of  the  fibrillar  segments  in  the 
several  stages  from  complete  relaxation  at  a  to  complete  contraction 
at  F.       (After  Eutherjord.) 

A.— &,  Bowman's  sarcous  elements ;  i,  intermediate  discs,  comprising  d,  granules 
of  Dobie  ;  /,  granules  of  Fli5?el ;  c,  clear  layer  between  it  and  end  of  sarcous 
element  (lateral  disc),  b,  I''frst  stai,'e  of  contraction  ;  the  clear  layer  be- 
tween Dobie's  granules  and  Fliiiirers' granules  on  the  one  side,  and  Fliigel's 
granules  and  the  end  of  the  sarcous  elements  has  disappeared.  F,  complete 
contraction, showing  sarcous  elements  comjiletely  shortened  :  accumulation 
of  chromatic  sulistauce  at  the  ends,  leaving  the  intervening  shaft  clear— 
Hansen's  median  disc. 

H 


yS  Elements  of  Histology. 

spoken    of   as    a    muscular    conipaitment    of    Krause 
{See  Fig.  65,  a). 

The  lateral  disc  contains  in  some  muscular  fibres 
{see  above)  a  layer  of  granules  or  rods,  the  secondary- 
disc,  or  Flogels  layer  ;  but  each  of  these  granules  or 
rods  is  ioined  to  a  granule  of  the 
.  51  i         intermediate     disc,     or    Dobie's 

^^^  |!  I        layer,    on  the  one  hand,  and  to 

1 1  \       the  end  of  a  sarcous  element  on 

,-       »*  \        the  other  ;  so  that  in  reality  it  is 

vL     11  I       a  thickening  of  the  bridges  con- 

V^    "-^         I        necting    the    ends    of  a    sarcous 
Vl    \\        I         element    to    the    granule    of  the 
V    11       I         intermediate  disc. 
^\\      •  The    transverse    disc,   or  the 

-  '*      \         laver  of  sarcous  elements,  shows 


m 


VV^  \      hardening,     or    after     treatment 
^\\  \     "^^'i^^  reagents,    a   median    trans- 
w\  5     verse   transparency,    due    to   the 


in   muscular   fibres    during    con- 
traction    (.y^e     below)     or     after 

1.1 

\\\\8     substance    of    the    sarcous    ele- 
"Wfi     ments    being    here    thinner,    as 
IllW    i^'-Pi^tioned    above.       This    corre- 
Fig.  GS.-Primitive    Mus-    ^ponds   to    the    median     disc    of 
euiar  Fibriiia;  from  the    Hensen.      Eutlierford,   however, 
Si'-^^S'f-     ^''■^'"'   pointed    out    that    this    appear- 
ance is  due   to  the  stainable  or 
chromatic  substance  of  each  sarcous  element  accumu- 
lating at  the  ends  (Figs.  66  and  67). 

In  muscular  fibres  treated  with  alcohol,  the  con- 
nection between  the  sarcous  elements  and  the  rest  of 
the  fibrillse  is  not  recognisable  ;  hence  the  muscular 
fibre  seems  split  up  into  discs,  apparently  not  con- 
nected with  one  another  {see  Fig.  60). 

The  reticulation  described  by  ^Nlelland,  ^Marshall, 
and  others  is  due  to  coagulation  of  the  sarcoplasma 


Striped  Muscular   Tissue. 


99 


brought  about  by  certain  hardening  reagents  ;  the 
sarcoplasma  between  the  granules  of  the  layer  of 
Dobie  or  Krause  would  thus  form  a  reticulated  disc 
extendinoj  transversely  across  the  muscular  fibre,  and 
to  it  are  joined  lines  of  coagulated  sarcoplasma  ex- 
tending longitudinally  between  the  sarcous  elements 
of  the  tibrill^  (Fig.  69). 

8''^.  During  contraction  the  transverse  striation  of 
the  tibre  becomes  much  narrower,  the  different  discs 
becoming  thinner  in  the 
long,  broader  in  the  trans- 
verse direction  of  the  fibre. 
In  the  naturally  contracted 
portion  of  a  muscular  fibre 
—  i.e.  at  the  point  of  the 
passage  of  the  contraction 
wave — the  stripes  alter  their 
character,  inasmuch  as  at 
the  end  of  the  transverse 
and  lateral  discs  the  fibres 
become  darker,  while  the 
middle  of  the  discs  of  sarcous 
elements  becomes  lighter. 
Whether  the  former  change 
— i.e.  of  the  lateral  discs — 
is  due  to  compression,  while 

the  latter — i.e.  of  the  sarcous  elements  —is  due  to  an 
imbibition  with  water  squeezed  out  of  the  sarcoplasma 
in  the  lateral  discs,  as  is  maintained  by  Engelmann, 
has  not  been  fully  established.  Rutherford,  on  the 
other  hand,  points  out,  what  appeal^  a  good  explana 
tion  of  this  phenomenon  — ^-iz.  of  the  so-called  re- 
versal of  the  stripes  during  contraction — that  during 
contraction  the  chromatic  substance  of  the  sarcous 
elements,  together  with  Flogel"s  granules  and  Dobie's 
granules,  forms  one  shortened  mass  ;  hence  the  darkness 
of   these    portions    in    each    fibrilla.     We    reproduce 


Fig.  69.— striped  Muscular  Fibres 
in  Cross-section.     {Altos.) 

Each  fibre  is  limited  by  the  sarco- 
lemiiia  ;  the  luuscular  substance 
is  differentiated  into  Cohnheim's 
areas. 


loo  Elemexts  of  Histology. 

here  from  Rutherford  drawinus  illustrating  these 
points  (Figs.  66  and  67). 

Rollett  considers,  with  Briicke,  Kolliker,  Engel- 
mann,  and  many  others,  that  the  fibrillar  are  the 
contractile  parts  :  while  Klihne,  Ramon  y  Cajal,  and 
others,  are  inclined  to  think  that  the  sarcoplasma — 
which  Kiihne  calls  sarcoglia— is  the  contractile  part, 
while  the  fibrillse — i.e.  the  rhabdia  of  Kiihne — or 
rather  the  sarcous  elements,  are  elastic  elements. 

The  differentiation  into  intermediate,  lateral,  and 
transverse  discs,  possessing  the  above-named  different 
structure  and  optical  properties,  produces  the  trans- 
verse striation  of  the  muscular  fibres  ;  but  it  must 
be  also  added  that  a  fibre,  though  homogeneous  but 
moniliform  (by  shrinking  or  naturally  so),  would 
show  a  transverse  striation  (Haycraft). 

89.  In  the  embryo  the  muscular  tibres  are 
developed  from  spindle-shaped  nucleated  cells  (Remak, 
Weissmann.  Kulliker).      One  spindle-shaped  cell  with 


"^--^.s^* 


Fig  70. — Striped  Muscular  Fibre  of  the  Diaphragm  of  a 
Guinea-pig.      {Atlas.) 

The  muscle  corpuscles  are  much  increased  iu  size  aud  numbers ;  tbey  are 
probably  used  here  for  the  new  formation  of  muscular  substance. 

an  oval  nucleus  grows  rapidly  in  length  and  thickness, 
its  nucleus  divides  repeatedly,  and  the  offspring 
become  shifted  from  one  another  as  the  cell  continues 
to  grow  in  lengtli.  Tlius  a  ]<»ng  spindle-shaped  mass 
of  sarcoplasma,  with  iiunierous  nuclei,   is  the  result. 


Striped  Muscular   Tissue.  ioi 

Tliis  sarcoplasiiia  in  the  middle  of  the  cell  becomes 
converted  into  fibrilhe,  and  this  formation  continues, 
while  the  sarcoplasma  as  a  whole  increases.  The 
muscle  corpuscles  of  the  adult  fibres  are  remains  of 
this  sarcoplasma  (Fig.  70). 

At  all  times  in  adult  life,  when  muscular  fibres 
increase  in  thickness,  as,  for  instance,  when  muscle 
is  kept  at  constant  work,  this  increase  is  due  to 
increase  of  sarco})lasma,  and  joart-conversion  of  this 
into  fibrillin. 

Paneth  described  in  fishes,  amphibia,  birds,  and 
mammals  a  mode  of  new  formation  of  muscular 
fibres  which  supplements  the  one  above  described. 
While  in  the  embryo  the  first  muscular  fibres  develop 
from  spindle-shaped  cells  in  the  manner  stated  above, 
muscular  fil^res  are  also  newly  formed  from  spherical 
or  oval  cells — sarcoplasts ;  in  the  interior  of  these 
cells,  the  protoplasm  is  converted  into  contractile 
substance,  which  is  capable  of  enlarging  and  elon- 
gating, and  becoming  converted  into  striped  muscular 
fil)res.  According  to  Kdlliker  and  Weissmann, 
muscle  fibres  divide  longitudinally  also,  so  that  one 
fibre  is  capable  of  giving  origin  to  a  bundle  of  thin 
fibres  each  of  which  continues  to  increase  in  thickness 
[see  muscle  spindles  below). 

90.  The  striped  muscular  fibres,  taken  as  a  whole, 
are,  as  a  rule,  spindle-shaped,  becoming  gradually 
thinner  towards  their  ends.  They  are  branched  in 
some  exceptional  cases — e.g.  in  the  tongue  ;  here  the 
extremities  of  the  muscular  fibres,  passing  into  the 
mucous  membrane,  become  richly  branched  previous 
to  their  terndnation  amongst  the  connective-tissue 
fibres  of  the  mucosa. 

91.  Muscular  fibres  terminate  in  tendons,  either 
by  the  whole  fibre  passing  into  a  bundle  of  connective- 
tissue  fibrils  (Fig.  71),  or  by  the  fibre  ending  abruptly 
with  a  Ijlunt,  conical  end,  and  becoming  here  fixed  to 


102 


Elements  of  Histology. 


from  one 


end 


FS 


a  bundle  of  cuunective-tissue  tibrils.  TJie  individual 
fibres  have  only,  as  has  been  mentioned  above,  a 
limited  lensth  :  so  that,  following  an  anatomical  bundle 
to  the  other,  we  tind  at  many  points 
along  the  fasciculus  some  muscle  fibres 
terminating,  others  originating.  This 
takes  place  in  the  following  way  :  the 
contents  of  a  fibre  suddenly  terniinate, 
while  the  sarcolemma,  as  a  fine  thread, 
becomes  interwoven  with  the  fine  con- 
necti\'e  tissue  between  the  muscular 
fibres.  Manv  muscles  contain  peculiar 
spindle-shaped  enlargements  ;  these  are 
the  muscle  buds  of  Kolliker  or  the 
inascle  spindles  of  Kiihne  ;  each  spindle 
is  a  bundle  of  fine  striped  muscular 
til  ires  formed  bv  lencjth  division  of  a 
mother  fibre,  and  enclosed  within  a 
thickened  connective  -  tissue  sheath, 
which  sheath  is  continuous  with  the 
laminated  connective  -  tissue  sheath 
(Henle's  sheath)  of  nerve  fibres — ^in 
fact,  the  sjfiiidles  occur  at  the  entrance 
of  certain  nerves  into  the  muscle  bundle 
[see  nerve  endings). 

92.  Tlie  striped  muscular  fibres  of 
the  heart  (auricles  and  ventricles)  and 
of  the  cardiac  ends  of  the  large  veins 
(the  pulmonary  veins  included)  differ 
from  other  striped  muscular  fil)res  in 
the  following  respects  : — -(1)  They 
possess  no  distinct  sarcolemma.  (2) 
Their  muscle  corpuscles  are  in  the  centre  of  the 
fibres,  and  more  numerous  than  in  ordinary  fibres. 
(3)  They  are  very  richly  branched,  each  fibre  giving 
oft"  all  along  its  course  short  branches,  or  continually 
dividinir    into    smaller    fibres    and     forming    a    close 


/ 


Fig.  71.  —  Two 
Striped  Mus- 
cular Fibres 
passing  into 
Bundles  of  Fi- 
brous Tissue. 
(Handbook.) 

(Termination  in 
Tendon.) 


Striped  Muscular  Tissue. 


ro3 


network  (l^'ig.  72).  A  transverse  section  tlirough  a 
bundle  of  such  fil)res  shows,  therefore,  their  cross- 
sections  irregular  in  shape  and  size.  (4)  Each  nucleus 
of  a  muscle  corpuscle  occupies  the  centre  of  one 
lU'isuiatic  portion  ;  each  fibre  and  its  branches  thus 
appear  composed  of  a  single  row  of  such  prismatic 
portions,  and  they  seem  separated  from  one  another — - 
at  any  rate  in  an 
early  stage  — by  a 
septum  of  a  trans- 
parent substance. 

93.  Some  mus- 
cular fibres  are 
either  markedly 
pale  or  markedly 
red  (Ranvier) ;  in 
the  former  {(ijj. 
quadratus  lumbo- 
rum,  or  adductor 
magnus  femoris  of 
rabbit)  the  trans- 
verse stria  t  ion  is 
more  distinct,  and 
the  muscular  cor- 
puscles less  nume- 
rous, than  in  the  ^ ' 
latter  (ejj.  semi- 
tendinosus  of  rabbit, 
diaphragm).  Here 
the  longitudinal 
striation  appears  very  distinct,  but  these  differences 
are  not  constant  in  the  same  fibres  of  other  animals 
or  of  man  (E.   jMeyer). 

94.  Briicke  has  shown  that  striped  muscular 
fibres  are  doubly  refractive,  or  anisotropous,  like 
uniaxial  positive  crystals  (rock  crystal),  the  optical 
axis  coincidini;  with  the  lonsc  axis  of  the  fibres.     The 


Z.— striped    Muscular    Fibres    of  the 
Heart. 

A,  Showinfe'  tlie  liniuching  of  the  fll)res  and  their 
anastomosis  in  networks;  b,  part  of  a  thin 
filire,  highly  mairnifled,  showing  the  raouili- 
forni  primitive  flbrillae;  c,  one  inimitive 
tibrilla  more  highly  magnified. 


I04  Elements  of  Histology. 

sarcoplasiiia  is  isotropous,  tlie  tibrilhr  alone  being 
anisotropoiis  ;  of  these  the  sarcous  elements  were  the 
first  recognised  by  Briicke  to  be  doubly  refractive. 
They  are,  however,  not  the  ultimate  optical  elements, 
but  must  be  considered  as  composed  of  disdiaclasts, 
the  real  doubly  refractive  elements  (Briicke). 


lo; 


CFI  AFTER    X. 


THE    HEART    AXD    BLOOD-VESSELS. 


95.   (a)  The   heart    consists  of  an   outer  serous 
covering,    tJie    visceral  pericardium    or     exocard,    an 
inner   lining,  the  endocardium,  and  Ijetween  the  two 
the    muscular    suh- 
stance      (Fig-      73). 
Underneath     the 
pericardium     is      a 
thin    layer    of   con- 
nective tissue  called 
the      subpericardial 
tissue. 

The  free  surface 
of  both  the  peri- 
cardium and  endo- 
cardium has  an  en- 
dothelial covering, 
like  other  serous 
membranes — i.e.  a 
single  layer  of  trans- 
parent nucleated  cell 
plates  of  a  more  or 
less  polygonal  or 
irregular  shape.  The 
groundwork  of  these 
two  membranes  is 
tibrous  connective 
tissue,     forming     a 

dense  texture,  and  in  addition  there  are  many  elastic 
fibres  arranged  as  networks.      Capillary  blood-vessels, 


Fit 


73. — Transverse    Section   through 
Auricle  of  the  Heart  of  a  Child. 


the 


a,  Endotbelium  lining  the  endocardium;  h,  en- 
docardium; c,  muscular  bundles  cut  trans- 
versely ;  d,  muscular  bundles  cut  longitudi- 
nally ;  e,  pericardial  covering  ;/,endotlieliuui. 


io6  Elements  of  Histology. 

lymphatic  vessels  and  small  Ijranclies  of  nerve  li))res 
are  met  with  in  the  pericardial  layer.  The  sub- 
pericardial  tissue  consists  of  trcibecula^  of  tibrous 
connective  tissue,  which  are  continuous  with  the 
intermuscular  connective  tissue  of  the  muscular  wall 
of  the  heart.  The  former  contains  in  many  places 
groups  of  fat  cells. 

96.  On  the  free  surface  of  the  papillary  muscles, 
in  some  parts  of  the  surface  of  the  trabeculse  carnese, 
and  at  the  insertion  of  the  valves,  the  endocardium  is 
thickened  by  tendinous  connective  tissue.  Each  valve 
is  covered  with  a  prolongation  of  the  endocard,  but 
the  main  body  of  the  valve  is  dense  tibrous  connective 
tissue ;  on  the  surface  of  this  connective-tissue  matrix 
is  a  somewhat  looser  connective  tissue,  containing 
also  a  few  elastic  fibres. 

All  the  corda3  tendineie and  the  \alves  are  of  course 
co\  ered  on  their  free  surfaces  with  endothelium. 

Special  tracts  of  uiuscle  fibies  occur  in  the  sub- 
endocardial tissue. 

The  fibres  of  Furkinje  are  peculiar  beaded  fibres 
occurrinor  in  the  subendocardial  tissue  in  some  mam- 
mals — e.g.  the  sheep  and  the  horse — and  birds  (not  in 
man).  They  are  thin,  transversely  striped,  muscular 
fil^res  possessed  of  local  thickenings  ;  the  central  part 
of  each  thickening  is  a  continuous  mass  of  protoplasm, 
with  nuclei  at  regular  intervals,  as  is  the  case  with 
some  skeletal  muscular  fibres  of  insects.  These 
beaded  fibres  of  Purkinje  must  not  be  confused  with 
the  inuscle  spindles  of  Kiihne. 

97.  The  muscular  fibres  forming  the  proper  wall 
of  the  heart,  the  structure  of  which  has  been  described 
in  the  previous  chapter,  are  grouped  in  bundles 
separated  by  vascular  fibrous  connective  tissue.  In 
the  ventricles  the  bundles  are  aggregated  into  more 
or  less  distinct  lamella?. 

Like   other  striped   muscular   fi'hres,  those  of  the 


Heart  and  Blood-vessef.s.  107 

wall  of  the  iieart  are  richly  supplied  with  blood-vessels 
and   lymphatics.      The   endocardium  and  valves  have 
no   blood-vessels   of   their   own,  but    the  pericardium 
possesses  its  own 
system  of  Idood-    ,   '•.-^n    C"^  '~^\  "^^v  - — ~     /'^^  --^ 

tics  form  a  peri-       Wi     ;j_j^'  -.==^^=.^^i^ 

cardial     and    an        ^^^^  _j;_^  _  ^.^^s^     """^^^^^^'^^ 

endocardial   net-    ^^^  fe— .^^         .=^^=s.  "^^ 

work    connected       g ^--^ss  -  _  ^^ 

with  the  lym- 
phatics of  the 
muscular  tissue 
of  the  heart ;  here 
there  are  lym- 
phatic clefts  be- 
tween the  mus- 
cular bundles, 
and  also  net- 
works of  tubular 

1  1     X-  fig.    74.— i^roin  a  xransverse  eectiou    tiii< 

i_)  inpuaiicb.  ^jjg  Inferior  Mesenteric  Artery  of  the  Pig. 

Jg,  inenerve      <>,  Endothelial  lining;  ?,  elastic  intinia;  m,  muscular 
l>.^Ti-./-l-.«c.     ,^^    ■*-!.«  media;      a,    adventitia    with  numerous    elastic 

Dianciies     Oi     ine  Ulinls,  cut  in  transverse  section.    (Af/a.s.) 

l^lexus  cardiacus 

torm  rich  plexuses.  In  connection  with  some  of  them 
are  found  numerous  collections  of  ganglion  cells  or 
ganglia.  These  are  very  numerous  in  the  nerve 
plexus  of  the  auricular  septum  of  the  frog's  heart 
(Ludwig,  Bidder),  and  in  tiie  auriculo-ventricular 
septum  of  the  frog  (Dogiel).  In  man  and  mammals 
numerous  ganglia  are  found  on  the  auricular  nerve 
branches,  chiefly  at  the  point  of  junction  of  the  large 
veins  with  the  heart,  Remak's  ganglia,  and  at  the 
boundary  between  the  auricles  and  the  ventricles, 
Bidder's  ganglia. 

91).   (b)  The  artoi-ieN  (Fig.  74)  consist  of  :   («)  an 


Fig.    74. — From  a  Transverse  Section    thiuugh 


[o8 


Elemexts  of  Histology. 


endotheliaJ  laijer  lining  the  lumen  of  the  vessel ;  (6)  an 
intima^  consisting  of  elastic  tissue  ;  (c)  a  media,  con- 
taining a  large  proportion  of  non-striped  muscular  cells 
arranged  chiefly  in  a  transverse,  i.e.  circular  manner ; 
and    [d)  an   adventitia    composed    chiefly   of    fibrous 

connective  tissue,  with 
an  admixture  of  net- 
works of  elastic  fibres. 

(«)  The  endothelium 
is  a  continuous  single 
layer  of  flattened  elon- 
gated cell  plates. 

(6)  The  intima  in 
the  aorta  and  larcje 
arteries  is  a  very  com- 
plex structure,  consist- 
ing of  an  innermost 
layer  of  fibrous  connec- 
tive tissue,  which  is  the 
"  inner  longitudinal 
fibrous  layer "  of  Re- 
mak,  outside  of  which 
^^^  is  a  more  or  less  longi- 

\^\  *~^^^^^^"  tudinally  arranged  elas- 

tic membrane.  This  is 
laminated,  and  com- 
posed of  fenestrated 
elastic  meinhranes  of 
Henle.  {See  page  61.) 
The  larger  the  arte^^y 
the  thicker  the  intima. 
In  microscopic  arteries 
the  intima  is  a  thin 
fenestrated  membrane,  the  fibres  having  distinctly  a 
longitudinal  arranfjement. 

(c)  The  media  is  the  chief  layer  of  the  wall  of  the 
arteries  (Fig.  75).     It  consists  of  transversely  arranged 


/ 


^ 


"^>*isa^> 


Fis. 


-Transverse  Section  through 
a  Microscopic  Artery  and  Vein  m 
the  Epiglottis  of  a  Child.     {Atlas. ) 

A,  The  artery,  showing  the  nucleated  en- 
dothelium, the  circular  muscular 
media,  aud  at  a  the  fibrous-tissue  ad- 
ventitia: V,  the  vein,  showing  the 
same  layers ;  the  media  is  very  Inuch 
thinner  than  in  the  arterv. 


Heart  and  Blood-vessels.  109 

clastic  laniellse  (fenestrated  membranes  and  networks 
of  elastic  tibres),  and  between  thern^  smaller  or  larger 
Ijundles  of  circularly  arranged  muscular  cells.  The 
larger  the  artery  the  more  elastic  tissue  is  there 
present  in  the  media,  the  smaller  the  artery  the  more 
muscular  tissue.  In  microscopic  branches  of  arteries 
the  media  consists  almost  entirely  of  circular  non- 
striped  muscle  cells  with  only  few  elastic  fibres, 

100.  In  the  last  branches  of  the  microscopic 
arteries  the  muscular  media  becomes  discontinuous, 
inasmuch  as  the  (circular)  muscular  cells  are  arranged 
not  as  a  continuous  membrane,  but  as  groups  of  small 
cells  (in  a  single  layer)  in  a  more  or  less  alternate 
fashion. 

When  the  media  contracts,  the  intima  is  thrown 
into  longitudinal  folds. 

The  aorta  has,  in  the  innermost  and  in  the  outer- 
most parts  of  the  media,  numbers  of  longitudinal 
and  oblique  muscle  cells.  According  to  Bardeleben, 
all  large  and  middle-sized  arteries  have  an  inner 
longitudinal  muscular  coat. 

101.  Between  the  media  and  the  next  outer  la3'er 
there  is^  in  larger  and  middle-sized  arterieS;  a  special 
elastic  membrane,  the  elastica  externa  of  Henle. 
(d)  The  adventitia  is  a  relatively  thin  fibrous  con- 
nective-tissue membrane.  In  large  and  middle-sized 
arteries  there  are  numbers  of  elastic  fibres  present, 
especially  in  the  part  next  to  the  media  ;  they 
form  networks,  and  have  chiefly  a  longitudinal 
direction. 

The  larger  the  artery  the  more  insignificant  is 
the  adventitia  as  compared  ^^•ith  the  thickness  of 
the  media. 

In  microscopic  arteries  (Fig.  76)  the  adventitia 
is  represented  by  thin  l)undles  of  fibrous  connective 
tissue  and  branched  connective-tissue  cells. 

Large  and  middle-sized  arteries  possess  their  own 


I  lO 


Elements  of  Histology. 


system     of    blood-vessels     (vasa 
chiefly    iu    the    adventitia    and 
vessels    and   lymphatic    clefts    are 
these  coats, 
102.   (c) 


vasorum),     situated 

media:    lymphatic 

also    present    in 


771  i.e 


fli 


^1  m 


11 


r^ 


3 


u 


'^ 


The  veiiisi  differ  from  the  arteries  in 
the  greater  thinness  of  their  wall.  The 
intima  and  media  are  similar  to  those 
of  arteries,  only  thinner,  both  abso- 
lutely and  relatively.  The  media  con- 
tains in  most  A^eins  circularly  arranged 
muscular  fibres ;  they  form  a  continu- 
ous layer,  as  in  the  arteries,  and  there 
is  between  them  generally  more  fibrous 
connective  tissue  than  elastic.  The 
adventitia  is  usually  the  thickest  coat, 
and  it  consists  chiefly  of  fibrous  con- 
nective tissue  (Fig.  75).  The  smallest 
veins — i.e.  before  passing  into  the 
capillaries — are  composed  of  a  lining 
endothelium,  and  outside  this  are  de- 
licate bundles  of  connective  tissue 
forming  an  adventitia.  The  valves 
of  the  veins  are  folds,  consisting  of  the 
endothelium  lining  the  surface,  of  the 
whole  intima,  and  of  j^art  of  the  mus- 
cular media. 

103.  There  are  many  veins  that 
have  no  muscular  fibres  at  all — e.g. 
vena  jugularis  (interna  and  externa), 
the  vena  -ubclavia,  the  veins  of  the  bones  and  retina, 
and  of  the  membranes  of  the  brain  and  cord.  Those 
of  the  gravid  uterus  have  only  longitudinal  muscular 
fibres.  The  vena  cava,  azygos,  hepatica,  spermatica 
interna,  renalis  and  axillaris,  possess  an  inner  circular 
and  an  outer  longitudinal  coat.  The  vena  iliaca, 
cruralis,  poplitea,  mesenterica,  and  umbilicalis  possess 
an  inner  and  outer  longitudinal  and  a  middle  circular 


n  I  fl  J<te'  i 


Fig.  76.— ilinnte 
Slicroscopic  Ar- 
tery.    {Atlas.) 

e,  Endotheliaru  ;  i. 
intima;  m,  mus- 
cular media.com- 
posed  of  a  siDgk- 
layer  of  circu- 
larly -  arranged 
non-striped  nius- 
cular cells;  a, ad- 
ventitia. 


Heart  axd  Blood-vessels.  iir 

muscular  coat.  Tlie  intiina  of  the  vena?  pulmonales 
in  man  is  connective  tissue  containing  circular  bundles 
of  non-striped  muscular  cells  (Stieda). 

104.  The  trunk  of  the  venie  pulmonales  and 
ven?e  cavre  possesses  striped  muscular  fibres,  these 
being  continuations  of  the  muscular  tissue  of  the 
auricles. 

105.  Hoyer  showed  that  a  direct  communication 
exists  between  arteries  and  veins  witliout  the  inter- 
vention of  capillaries— as  in  the  matrix  of  the  nail, 
in  the  tip  of  the  nose  and  tail  of  some  mammals,  in 
the  tip  of  the  fingers  and  toes  of  man,  in  the  margin 
of  the  ear  lobe  of  dog  and  cat  and  rabbit. 

In  the  cavernous  tissue  of  the  genital  organs 
veins  form  large  irregular  sinuses,  the  wall  of 
which  is  formed  by  fibrous  and  non-striped  muscular 
tissue. 

lOG.  (d)  The  capillary  blood-vessels  are 
minute  tubes  of  about  a^oVo  ^^  Wiro  *^^  ^'^  inch  in 
diameter.  Their  wall  is  a  single  layer  of  transparent 
elongated  endothelial  plates,  united  by  thin  lines  of 
cement  sidistance  (Fig.  77).  Each  cell  has  an  oval 
nucleus  ;  in  fact,  the  wall  of  the  capillaries  is  merely 
a  continuation  of  the  endothelial  membrane  linins: 
the  arteries  and  veins. 

In  some  places  the  capillaries  possess  a  special 
adventitia  made  up  of  branched  nucleated  connective- 
tissue  cells  (hyaloidea  of  frog,  choroidea  of  mammals), 
or  of  an  endothelial  membrane  (pia  mater  of  brain 
and  cord,  retina  and  serous  membranes),  or  of  adenoid 
reticulum  (lymphatic  glands,  His). 

The  smallest  capillaries  are  found  in  the  central 
nervous  system,  the  largest  in  the  marrow  of  bone. 
The  capillaries  form  networks,  the  richness  and 
arrangement  of  which  vary  in  the  different  organs, 
according  to  the  nature  and  arrangement  of  the 
elements  of  the  tissue  (Fig.  78). 


1  12 


Elements  of  Histology 


107.    If   capillaries  are   abnormally  distended,  as 
ill    inflammation,    or    otherwise    injured,    the   cement 


fc^'<-r 


Fig.  77.-  From  a  Preparation  of  the  Peritoneum,  stained  ^vitli 
Nitrate  of  Silver.    (Handbook.) 

a,  Entlotlieliuin  on  the  free  surface  of  the  membrane  ;  h,  capillary  blood  sessels 
in  the  membrane  ;  their  wall  is  a  layer  of  eQclotbelium. 


Fig.  78.— Young  Fat  Tissue  of  the  Omentum,  its  Blood-vessels  injected. 
n.  Artery  ;  b,  vein ;  r,  network  of  capillariei?.    {Handbook.) 

substance  between  the  endothelial  plates  is  liable  to 
o-ive  way  in  tlie  shape  of  minute  holes,  or  stigmata, 


Heart  and  Blood-vessels. 


i»3 


\\  liicli  in;iyl>econie  lur^er  holes,  or  *•^(J'/y<^(^^  Tlie  passage 
of  red  bloofl  cori)uscles  (diapedesis)  and  the  migration 
of  wJiite  corpuscdes  in  inflammation  through  the  un- 
broken capillaries  and  small  veins  occur  through 
these  stigmata  and  stomata. 

108.  Yoiiii^:  and  g^row  iiig^  capillaries,  Ijoth 
of  normal  and  pathological  tissues,  possess  solid  thread- 
like shorter  or  longer  nucleated  protoplasmic  processes 
(Fig.   79),   into  which  the    canal  of  the   capillary  is 


Fig.  70.  —From  a  Pi-eparation  of  Omentum  of  Rabbit,  after  staining  with 
Xitrate  of  Silver.    {Atkis.) 

V,  Minute  vein  ;  a,  solid  protoplasmic  prolongations  of  the  wall  of  a  capillary, 
connected  with  connective-tissue  corpuscles  ;  c,  solid  young  bud. 

gradually  prolonged,  so  that  the  thread  becomes  con- 
verted  into  a  new  capillary  branch.      Such   growinor 
capillaries  are  capable  of  contraction  (Strieker). 
All  blood-vessels,   arteries,  veins,  and  capillaries. 


114 


Elements  of  Histology 


d    fibrous    connective-tissue 


both  in   the  embryo  and 


ill  their  early  .stages,  both  ill  embryonal  and  adult 
life,  are  of  the  nature  of  minute  tubes,  the  wall  of 
which  consists  of  a  simple  endothelial  membrane.  In 
the  case  of  the  vessel  becoming  an  artery  or  vein, 
cells  are  added  to  the  outside  of  the  endothelium, 
thus  forming  the  material  for  the  development  of 
the  elastic,  muscular,  and 
elements  of  the  wall. 

109.  In  the  first  ;• 
in  the  adult,  the  vessel  is  re^jresented  by  solid  nucle- 
ated protoplasmic  cells,  spherical,  elongated,  spindle- 
shaped,  or  bran- 
ched —  vasofor- 
iiiative  cells. 
Such  cells  may 
be  isolated  and 
indej)endent  of 
any  pre-existing 
vessel,  or  they 
ma}^  be  solid 
prot  opl  as  mic 
outgrowths  of 
the  endothelial 
wall  of  existing 
capillarv  vessels 
(Fig.  80).  In 
both  cases  they 
become  hollowed 
out  by  a  process 
of  vacuolation  ; 
isolated  vacuoles 
appear  at  first, 
but  tliev  oradu- 
ally  become  Oion- 
iiuent,  and  thus  a  young  vessel  is  formed,  at  first 
very  irregular  in  outline,  but  gradually  acquiring 
more  and   more  of  a   tulnilar  form.      In  the  case  of 


so. — Developing  Capillary  Blood-vessels  from 
the  Tail  of  Tadpole.      {Atlas.) 

V,  Capillary  vein  with  clumps  of  pigiueat  in  the 
■wait :«,  nucleated  protoplasmic  sprouc  ;  /.solid 
anastomosis  between  two  neighbouring  capil- 
laries. 


Heart  and  Blood-vessels. 


11^ 


ail  isolated  cell,  its  protoplasmic  processes  grow  l)y 
degrees  to  th(!  nearest  capillary,  to  the  wall  of  which 
they  become  fixed,  and  the  cavity  of  the  cell  finally 
opens  through  such  processes  into  that  of  the  capillary 
vessel. 

The  islets  or  cysts  of  blood  that  appear  early  in  the 
area  vasculosa  of  the  embryo  are  due  to  vacuolation  of 


Fig.  SI.— Cells  from  inesoblast  of  chick's  blastoderm  undergoing  develop- 
ment into  blood-vessels  in  the  area  vasculosa.     (Handbook.) 

",  Cavitj-  of  cell;  b,  cell  wall ;  /,  cells  not  yet  hollowed  out ;  d,  hlood  corpuscles. 


spherical  or  elongated  vasoformative  cells  of  the  meso- 
blast,  the  islets  or  cysts  being  composed  of  a  central 
portion  which  are  blood  corpuscles,  at  first  white,  then 
red,  and  a  joeripheral  protoplasmic  nucleated  envelope, 
the  future  vascular  wall.  The  central  nucleated  blood 
cells  develop  by  a  process  of  endogenous  division  from 
the  original  cell  protoplasm.  The  blood  cysts,  at  first 
isolated,  afterwards  become  connected  by  protoplasmic 
processes  with  other  cysts  or  other  vasoformative  cells, 
ultimately  forming  a  network  of  vessels  (Fig.  81). 

The.  wall  of  young  capillaries  is  granular-looking 
})rotoplasm   (the    original  cell  substance),    and    in    it 


ii6  Elements  of  Histology. 

are  disposed,  in  uiore  or  less  regular  fashion,  oblong 
nuclei,  derived  Ijv  multiplication  from  the  nucleus  of 
the  orkdnal  cell.  In  a  later  stai:e.  a  differentiation 
takes  place  in  the  protoplasmic  wall  of  the  capillary 
into  cell  plates  and  cement  substance,  in  such  a  way 
that  each  of  the  above  nuclei  appertains  to  one  cell 
plate,  which  now  represents  the  linal  stage  in  the 
formation  of  the  capillary.  Both  in  the  embryo  and 
in  the  adult  a  few  isolated  nucleated  protoplasmic  cells, 
or  a  few  protoplasmic  solid  processes  of  an  existing 
capillary,  may  by  active  and  continued  growtli  give 
origin  to  a  whole  set  of  new  capilkries  (Strieker, 
Aftanasieff".  Arnrild.  Klein,  Balfour,  Ranvier,  Leboucq). 


I  T 


CHAPTER   XI. 


THE    LYMPHATIC    VESSELS. 


110.  The  larg^e  lymphatic  trunks,  such  as  the 
thoracic  duct,  and  the  lymphatic  vessels  passing  to  and 
from  the  lymphatic  glands,  are    thin-walled    vessels, 


Fig.  82. — Lymphatic  Vessels  of  the  Diaphragm  of  the  Dog,  stained  with 
Nitrate  of  Silver.     (Atlofi.) 

The  eadothelium  foniiin','  tlie  wall  of  tlie  lymphatics  is  well  shown  ; 
V,  valves. 

siaiilar  in  structure  to  arteries.  Their  lining  endo- 
thelium is  of  the  same  character  as  that  of  an  artery, 
and  so  are  the  elastic  intima  and  the  media  with  its 
circular  muscular  tissue  ;  but  these  latter  are  very 
much  thinner  than  in  an  artery  of  the  same  calibre. 


ii8 


Elements  of  Histology 


a 


Tlie  ach  entitia  is  an  exceedingly  thin  connective- 
tissue  membrane  with  a  few  elastic  fibres.  Tiie 
valves  are  semi-lunar  folds  of  the  endothelium  and 
intima, 

111.  The  lyiiipliatics  in  the  tissues  and  organs 
form  rich  plexuses.  They  are  tubular  vessels,  the 
wall  of  which  is,  like  that  of  a  capillary  blood-vessel, 

a  single  layer  of  endothelial 
plates  (Fig.  82).  The  lym- 
phatic is  often  many  times 
wider  than  a  blood  capillary. 
Tlje  endothelial  plates  are  elon- 
gated, but  not  so  long  as  in  a 
Ijlood  capillary,  with  more  or 
less  sinuous  outlines  :  but  this 
depends  on  the  amount  of 
shrinking  of  the  tissue  in  which 
tlie  vessel  is  embedded  :  when 
there  is  no  shrinking  in  the 
tissue  or  in  the  vessel,  the  out- 
lines of  the  cells  are  more  or 
less  straight. 

The  lymphatics  are  sup- 
ported by  the  tibrous  connective 
tissue  of  the  surrounding  tissue, 
which  does  not,  however,  form 
part  of  their  wall 

112.     The    outline    of    the 

vessel  is  not  straight,  but  more 

or    less    moniliform,    owing    to 

Fig. 83. -From silver-stained   tlie    slight    dilatations    present 

specimen  of  the  mesentery   l^elow    and    at    the    senii-lnnar 

of  tne  fro*" 

o.     Artery;  %.     perivascular     VfdceS:      thcSC    are    folds   of    the 

iffendoibHiar'vaa  "'"'''^  endothelial   wall,  and  they  are 

met     with     in    great    numbers. 

The  vessel   apjiears  slightly  dilated  innnediately  be- 

vond  the  valve — that  is,   on   the   side  farthest  from 


LvMPffAT/c   Vessels.  119 

the    peripliery,    or   rootlet,    whence    the    current    of 
lymph  starts. 

il3.  Tracing  the  lymphatic  vessels  in  the  tissues 
and  organs  towards  their  rootlets,  we  come  to  more  or 
less  irregularly-shaped  vessels,  the  wall  of  which  also 
consists  of  a  single  layer  of  polygonal  endothelial 
])lates;  the  outlines  are  very  sinuous.  These  are  the 
IjimpJtatic  capUJaries  ;  in  .some  places  they  are  mere 
clefts  and  irregular  sinuses,  in  others  they  have  more 
the  character  of  a  tube,  but  in  all  instances  they 
have  a  complete  endothelial  lining,  and  no  valve.s. 

Sometimes  a  blood-vessel,  generally  arterial,  is 
ensheathed  for  a  shorter  or  longer  distance  in  a 
lymphatic  tube,  which  has  the  character  of  a  lym- 
l»hatic  capillary ;  these  are  the  perivascular  hjm- 
pliatics  of  His,  Strieker,  and  others  (Fig.  83). 

114.  The  rootlets  of  the  lyiiiphatic!^  are  situ- 
ated in  the  connective  tissue  of  the  different  origans 
in  the  shape  of  an  intercommunicating  system  of 
crevices,  clefts,  spaces,  or  canals,  existing  between  the 
bundles,  or  groups  of  bundles,  of  the  connective  tissue. 
These  rootlets  are  generally  without  a  complete  endo- 
thelial lining,  but  are  identical  with  the  spaces  in 
which  the  connective-tissue  corpuscles  are  situated  ; 
N\here  these  are  branched  cells  anastomosing  by  their 
processes  into  a  network — such  as  the  cornea,  or 
serous  membranes — we  tind  that  the  rootlets  of  the 
lymphatics  are  the  lacunse  and  canaliculi  of  these  cells 
— the  typical  lymph- canalicular  system  of  von 
Recklinghausen  (Fig.  84).  The  endothelial  cells 
forming  the  wall  of  the  lymphatic  caj^illaries  are 
directly  continuous  with  the  connective  cells  situated 
in  the  rootlets.  In  tendons  and  fascife  the  minute 
lymphatics  lie  between  the  bundles,  and  have  the 
shape  of  continuous  long  clefts  or  channels  ;  in 
striped  muscular  tissue  they  have  the  same  character, 
being  situated  l^etween  the  muscular  fibres. 


I  20 


Elements  of  HjsroLOGV. 


The  passage  of  plasma  from  the  minute  arteries 
and  capiUarv  blood-vessels  into  the  lymph-rootlets 
situated  in  the  tissues,  and  thence  into  the  lymphatic 


Fig.  S4-  From  silver-stained  preparation  of  the  Central  Tendon  of  the 
Rabbit's  Diaphragm,  showing  the  direct  connection  of  the  Lyniph- 
canalicular  System  of  the  Tissue  with  the  Lymphatic  Capillaries. 

a.  LympUatlc  vessel;  h,  lymphatic  capillary  lined  wich  "sinuous'  endotheliom. 

(Handbook.) 

capillaries  and  lymphatic  vessels,  represents  the  natural 
current  of  Ivmph  irrigating  the  tissues. 

115.  Lymph  cavities. — In  some  cases  the  lym- 
phatic vessels  of  a  tissue  or  organ  are  possessed  of,  or 
connected  with,  irregularly-shaped  large  sinuses,  much 
wider  than  the  vessel  itself  :  these  cavities  are  the 
lymph  sinuses,  and  their  wall  is  also  composed  of  a 


Lymphatic   Vessels. 


I  2  I 


single  layer  of  more  or  less  polygonal  endothelial 
plates  with  very  sinuous  outlines.  Such  sinuses  are 
found  in  connection  with  the  subcutaneous  and  sub- 
mucous lymphatics,  in  the  diaphragm,  mesentery,  liver, 
lungs,  etc.  On  the  same  footing — i.e.  as  lymph 
sinuses — stand  the  comparatively  large  lymph  cavities 
in  the  body,  such  as  the  subdural  and  subarachnoidal 
spaces  of  the  central  nervous  system,  the  synovial 
cavities,  the  cavities  of  the  tendon-sheaths,  the  cavity 
of  the  tunica  vaginalis  testis,  the  pleural,  pericardial, 
and  peritoneal  cavities.  In  batrachian  animals — e.g. 
frogs — the  skin  all  over  the  trunk  and  extremities  is 
separated  from  the  subjacent  fascipe  and  muscles  by 
large  bags  or  sinuses — the  subcutaneous  lynipJi  sacs. 
These  sinuses  are  shut 
off  from  one  another 
by  septa.  Between  the 
trunk  and  the  extremi- 
ties, and  on  the  latter, 
the  septa  generally 
occur  in  the  region  of 
the  joints.  In  female 
froiifs  in  the  mesoo-as- 
trium  smaller  or  larger 
cysts  lined  with  cili- 
ated endothelium  are 
sometimes  found.  Be- 
hind the  peritoneal 
cavitv  of  the  fros:,  on 
each  side  of  the  ver- 
tebral column,  exists  a 
similar  large  lymph  si- 
nus, called  the  cisterna 
lyniphatica  magna. 

116.  The  lymph  cavities  are  in  all  instances  in  direct 
communication  with  the  lymphatics  of  the  surround- 
ing parts   by  holes  or  open  mouths  (stomata),  often 


Fi; 


.  8.J.  — Stuinata,  lined  witli  Gennina- 
ting  Endothelial  Cells,  as  seen  froni 
the  Cisternal  Surface  of  the  Septuni 
Cisternal  I.yniphatici«  Magnai  of  the 
Frog.     (Hundboolc.) 


122 


Elements  of  Histology. 


surrounded  by  a  special  layer  of  polyLedral  endothe- 
lial cells — germinating  cells  (Figs.  85,  %^).  Such 
stomata  are  numerous  on  the  peritoneal  surface 
of  the  central  tendon  of  the  diaphragm,  in  which 
are  found  straight  lyn)ph  channels  between  the  tendon 
bundles,  and  these  channels  communicate  by  nu- 
merous stomata  with 
the  free  surface.  A 
similar  arrangement 
exists  on  the  costal 
pleura,  the  omentum, 
and  the  cisterna  Ivm- 
phatica  magna  of  the 
frog.  {See  Chapter 
IV.) 

117.  The  serous 
uieiiibraiies  con- 
sist of  endothelium 
upon  a  layer  of 
fibrous  tissue  with 
networks  of  line 
elastic  fibres  :  they 
contain  networks  of 
])lood  capillaries  and  numerous  lymphatic  vessels 
arranged  in  (superficial  and  deep)  plexuses.  Plexuses 
of  lymphatics  are  very  numerous  in  the  pleura  costalis 
— or  rather,  intercostalis — in  the  diaphragm  and  pleura 
pulmonalis.  They  are  important  in  the  process  of 
absorption  from  the  pleural  and  peritoneal  cavity 
respectivelv.  Lymph  and  lymph  corpuscles,  and  other 
solid  particles,  are  readily  taken  uj:)  by  the  stomata 
{see  Fig.  31)  and  brought  into  the  lymphatics.  Here 
the  respiratory  movements  of  the  intercostal  muscles, 
of  the  diaphragm,  and  of  the  lungs  respectively,  pro- 
duce the  result  of  the  action  of  a  pump. 

118.   There  exists  a  definite  relation  between  the 
lymphatics  on  the  one  hand  and  the  epithelium  on  the 


Fig.  86. — Endotheliuia  ami  Stomata  of  tlie 
Peritoneal  Surface  of  the  Septum  Cis- 
ternse  Lj-mpbaticte  Magnge  of  the  Frog. 
{Hawlhook.) 


Lymphatic   Vessels.  123 

other,  wliieli  covers  the  mucous  membranes  and  lines 
the  various  glands,  and  also  between  the  endothelium 
covering  serous  membranes  and  that  lining  their  vessels 
and  lymph  cavities — namely  this:  the  albuminous  semi- 
fluid cement  substance  {see  former  chapters)  between 
the  epithelial  or  endothelial  cells  is  tlie  path  by  which 
fluid  and  formed  matter  passes  between  the  surfaces 
and  the  lymph-canalicular  system — i.e.  the  rootlets  of 
the  lymi)liatics. 

119.  L.yiiii>li  taken  from  the  lymphatics  of  difl^er- 
ent  regions  differs  in  composition  and  structure.  That 
from  the  thoracic  duct  contains  a  large  number  of 
colourless  or  white  corpuscles  (lymph  corpuscles),  each 
of  which  is  a  protoplasmic  nucleated  cell  similar  in 
structure  to  a  white  blood  corpuscle.  They  are  of 
various  sizes,  according  to  the  stage  of  ripeness.  The 
smaller  lymphocytes  contain  one,  some  of  the  larger  con- 
tain two  and  three  nuclei  corresjDonding  to  the  typical 
leucocytes.  The  latter  show  more  pronounced  amoeboid 
movement  than  the  former.  Also  "granular  "  oxyphile, 
basophile,  and  amphophile  cells  are  met  with  amongst 
the  leucocytes.  A  few  red  corpuscles  are  also  met 
with.  Granular  and  fatty  matter  is  present  in  large 
(|uantities  during  and  immediately  after  digestion. 

In  the  frog  (and  also  in  other  lower  vertebrates — 
e.g.  reptiles)  there  exist  certain  small  vesicular  lymph 
cavities,  about  an  eighth  of  an  inch  in  diameter, 
which  show  rhythmic  pulsation  ;  they  are  called  lym^^li 
hearts.  On  each  side  of  the  os  coccygis  and  under- 
neath the  skin  is  a  pulsating  posterior  lymph  heart. 
The  anterior  lymph  heart  is  oval,  and  is  situated  on 
each  side  of  the  processus  transversus  of  the  third  and 
fourth  vertebrae  ;  it  is  rather  smaller  than  the  posterior 
one.  Each  lymph  heart  has  afferent  lymphatics,  by 
which  it  is  in  open  communication  with  the  lymph- 
atics of  the  periphery,  and  from  it  passes  out  an  efferent 
vessel  which  opens  into  a  large  vein  (a  l)ranch  of  the 


124 


Elements  of  Histology. 


sciatic  and  jugular  veins  resiDeetively).  A  valve 
allows  Ivmpli  to  flow  out  of  the  lymph  heart  into 
the   vein,   but   pre\'ents  regurgitation  of  blood  from 


Fig.  87. — Developing  Lyinph-capillaries  in  the  Tail  of  Tadpole.     {Atlas.) 
a,  Solid  nucleated  protoplas  iiic  branches  not  yet  hollowed  out. 


the  vein.  The  i?iternal  surface  of  the  lymph  hearts 
is  lined  with  an  endothelium  like  the  lymph  sacs,  and 
in  their  wall  they  possess  plexuses  of  striped,  branched, 
muscular  fibres.  The  nerve  fibres  terminate  in  these 
striped  muscular  fibres  in  the  same  manner  as  in  those 
of  other  localities.      (Ranvier.) 


L  YMPHA  TIC   Vessel  s.  125 

12U.  Lvm})liatic  vessels  are  developed  and  newly 
formed  under  normal  and  pathological  conditions  in 
precisely  the  same  way  as  blood-vessels.  The  accom- 
panying woodcut  (Fig.  87)  shows  this  very  well.  AVe 
have  also  here  to  do  with  the  hollowing  out  of  (con- 
nective tissue)  cells  and  their  processes  previously 
solid  and  protoplasmic. 


126 


CHAPTER     XII. 

FOLLICLES    OR    SIMPLE   LYMPH    fiLAXDS. 

121.  Under  this  name  ^ve  include  the  blood  glands, 
or  the  conglobate  gland  substance  of  Hewson,  His, 
and  Henle.  or  the  lymph  follicles  (Kolliker,  Huxley, 
Liischka).  The  ground  sul)staneeof  all  lymph  glands, 
simple  as  well  as  compound  (see  below),  is  the  lymph- 
atic or  o.denoid  tissue,  or  leucocvtocrenous  tissue. 
Like  all  other  gland  tissue,  it  is  supplied  with  a  rich 
network  of  capillaries  derived  from  an  afferent 
artery,  and  leading  into  ett'erent   veins. 

122.  The  elements  constituting  this  tissue  are  : — 
(«)   The  adenoid  reticnlura   (Fig.  88),   a  network 

of  tine  homogeneous  fibrils,  with  numerous  plate-like 
enlargements. 

(b)  SiiiaU,  transparent,  fljif,  endotlteloid  cell phites, 
each  with  an  oval  nucleus.  These  cell  plates  are  fixed 
on  the  reticulum,  of  which  at  first  sight  they  seem 
to  form  part.  Their  oval  nucleus  especially  ap[)ears 
to  belong  to  a  nodal  ])oint — i.e.  to  one  of  the 
enlargements  of  the  reticuluni  :  l>ut  bv  continued 
shaking  of  a  section  of  any  lymphatic  tissue,  the  oval 
nuclei  and  their  cell  plates  can  be  got  rid  of,  so  that 
onlv  the  n^riculum  is  left,  without  any  trace  of  a 
nucleus. 

(c)  Lymph  rorpiLScles  completely  fill  the  meshes  of 
the  adenoid  reticulimi.  These  can,  however,  be  easily 
shaken  out.  They  are  of  different  sizes  ;  some^the 
young  ones — are  small  cells,  with  a  comparatively 
large  nucleus  ;  others — the  ripe  ones — are  larger, 
have  a  distinct  protoplasmic  cell   body,  with  one  or 


S/MFLK  Lymphatic  Glands. 


127 


two  nuclei.  Ill  all  lyini)hatic  tissues,  be  they  part  <jt" 
a  simple  or  ot"  a  compound  lymph  glantl,  certain  parts 
are  ot"  greater  transparency  than  others,  due  to  the 
lymph      cells 

being     larger  ..        ..  1.  '^\       J 

and  in  a  state 
of  division,  as 
indicated  by 
the  various 
phasesofmito- 
tic  division  of 
their  nucleus 
(  F 1  e  ni  m  i  n  g, 
Heilbrunn). 
These  parts 
form,  there- 
fore, centres 
of  germina- 
tion, and  con- 
stitute what 
are  spoken 
of  as  yenn 
c  e  litres,    or 

germ  nodules  (Flemming).  The  germ  centres  are 
not  permanent  structures. 

123.  The  adenoid  tissue  occurs  as  : 

(1)  Diffuse  adenoid  tissue,  without  any  detinite 
arrangement.  This  occurs  in  the  subepithelial  layer 
of  the  mucous  membrane  of  the  nasal  fossae  and 
trachea,  in  the  mucous  membrane  of  the  false  vocal 
cords  and  the  ventricle  of  the  larynx,  in  the  posterior 
})art  of  the  epiglottis,  in  the  soft  palate  and  tonsils, 
at  the  root  of  the  tongue,  in  the  pharynx,  in  the 
mucosa  of  the  small  and  large  intestine,  including  the 
villi  of  the  former ;  and  in  the  mucous  membrane  of 
the  nasal  cavity  and  vagina. 

{'!)  Cords,  cijUnders,  ov  [xitclf-^  of  adenoid  tissue; 


Fig.  SS. — Adenoid  Reticulum  shaken  out ;  most  of 
the  Lymph  corpuscles  are  removed.  From  a  Lym- 
phatic Gland.     {Atlo^.) 

a,  Reticulum  ;  c,  capillary  blood-vessel. 


128 


Elements  of  Histology 


ill     the     omentum     and    pleura,    and    in    the    spleen 
(^[alpigliian  corpuscles). 

(3)  Lymph  follicles,  i.e.  oval  or  spherical  masses 
more  or  less  well  detined  ;  in  the  tonsils,  at  the  root 
of  the  tongue,  in  the  u[)per  part  of  the  pharynx 
(phar3'nx  tonsil),    in  the    stomach,    small    and    large 


Fig.  89.  —  Lyinphangial  Nodules, in  the  Omentum  of  a  Guinea-pig,  developini: 
in  connection  with  lymph  vessels.     {Klein's  "  Lymphatic  Sydevi.") 

A,  Perilymphangial  nodule:  a.  lymph  vessel;  b,  lymphoid  tissue:  c,  its  enclo- 
thelial  wall;  t',  Tilood  capillaries:  b:  endolyraphanarial  structure:  a,  vein  ; 
b,  artery;  c,  capillaries  ;  d,  perivascular  lymph  vessel ;  e,  lymphatic  tissue; 
/,  endothelial  wall  of  the  lymph  vessel. 


intestine ;  in  the  nasal  mucous  membrane,  in  the 
large  and  small  bronchi  ;  and  in  the  spleen  (Mal- 
pighian  corpuscles). 

Most  of  these  masses  of  adenoid  tissue  mentioned 
hitherto  are  developed  in  the  wall  or  even  in  the 
cavity  of  a  lymph  vessel  or  lymph  sinus  as  pei'i-  and 
endo-lymphanr/ial  nodules ;  in  the  former  case  the 
lymph    tissue   remains    surrounded   for  a  smaller  or 


Simple  Lymphatic  Glands. 


129 


l;ir<,^u'  part  of  its  periphery  by  a  lymph  siuus  formini^ 
l)art  of  a  network  of  lyin[>li  tubes  (Fig.  89,  a  and  b). 
124.  The  tonsils  (Fig.  90)  are  masses  of  lymph 
follicles  anil  diflfase  adenoid  tissue  covered  with  a  thin 
mucous  membrane,  which  penetrates  in  the  shape  of 


•  ■•'.**,■•'.'. 


;'-'^i',\ 


/■'  -^    ■^'^^^:  --'  III 

Fig.  90.— Vertical  Sectiun  through  part  of  the  Tuiisil  of  Dog.     {AUo.s.) 

e.  Stratified  pavement  epitbelluni  covering  tbe  free  surface  of  the  raucous 
membrane.  The  tissue  of  the  mucous  membrane  is  infiltrated  wiih  adenoid 
tissue.  /,  lymph  follicles ;   m,  raucous  gland  of  tbe  submucous  tissue. 

longer  or  shorter  folds  into  the  substance  within. 
Numbers  of  mucus-secreting  cjlands  situated  outside 
the  layer  of  lymph  follicles  discharge  their  secretion 
into  the  pits  (the  crypts)  between  the  folds.  The  free 
surface  of  the  tonsils  and  the  crypts  is  covered  or 
lined  with  similar  stratified  epithelium  to  that  which 
lines  the  oral  cavity.      Xumbers  of  lymph  corpuscles 


130  Elements  of  Histology. 

constantly,  in  the  perfectly  normal  condition,  migrate 
through  the  epithelium  on  to  the  free  surface,  and  are 
mixed  with  the  secretions  (mucus  and  saliva)  of  the 
oral  cavity.  The  so-called  mucous  or  salivary  cor- 
puscles of  the  saliva,  taken  from  the  oral  cavity,  are 
such  discharged  lymph  corpuscles  (Stohr).  They 
become  swollen  up  by  the  water  of  the  saliva,  and 
assume  a  spherical  shape.     They  finally  disintegrate. 

Similar  relations,  only  on  a  smaller  scale,  obtain 
at  the  root  of  the  tongue. 

The  pJuirynx  tonsil  of  Luschka,  occurring  in  the 
upper  part  of  the  pharynx,  is  in  all  essential  respects 
similar  to  the  palatine  tonsil.  Owing  to  large  parts 
of  the  mucous  membrane  of  the  upper  portion  of  the 
pharynx  being  covered  with  ciliated  columnar  epi- 
thelium, some  of  the  cryptr:  in  the  pharynx  tonsil  are 
also  lined  w4th  it. 

125.  The  lenticular  g-laiitl*^  of  the  stomach  are 
single  lymph  follicles. 

The  solitary  glands  of  the  small  and  large 
intestine  are  single  lymph  follicles. 

The  agniinated  g-lands  of  the  ileum  are  groups 
of  lymph  follicles.  The  mucous  membrane  containing 
them  is  much  thickened  by  their  presence.  These 
groups  of  follicles  are  called  a  Peyer^s  ixitcli  or  a 
Peyers  gland  (see  Intestine). 

126.  In  most  instances  the  capillary  blood-vessels 
form  in  the  lymph  follicles  meshes,  arranged  in  a  more 
or  less  radiating  manner  from  the  periphery  towards 
the  centre ;  around  the  periphery  there  is  a  network 
of  small  veins.  A  larger  or  smaller  portion  of  the 
circumference  of  the  follicles  of  the  tonsils,  pharynx, 
intestine,  bronchi,  etc.,  is  surrounded  by  a  lymph 
sinus  leading  into  a  lymj)hatic  vessel.  (See  above.) 
The  lymphatic  vessels  and  lymph  sinuses  in  the 
neighbourhood  of  lymphatic  follicles  or  of  diffuse 
adenoid  tissue    are    almost    always  found  to  contain 


Simple  Lymphatic  Glands.  131 

numerous  lymph  corpuscles,  thus  indicating  that 
these  are  produced  by  the  adenoid  tissue  and  absorbed 
by  the  lymphatics. 

r27.   The  tliyiiiiiH     ^laiid   consists  of  a  frame- 


'*   ■"    =«  to   '^  " 

Fig.  91.— Section  through  the  Thymus  Gland  of  a  Fcetus. 

a.  Fibrous  tissue    between  the  follicles;   &,  cortical  portion   of  the  follicles 
c,  medullary  portion. 


work  and  the  gland  substance.  The  former  is  fibrous 
connective  tissue  arranged  as  an  outer  capsule,  and 
in  connection  with  it  are  septa  and  trabeculae  passing 
into  the  gland  and  subdividing  it  into  lobes  and 
lobules,  which  latter  are  again  subdivided  into  the 
follicles  (Fig.  91).  The  follicles  are  very  irregular 
in  shape,  most  of  them  being  oblong  or  cylindrical 
streaks  of  adenoid  tissue.  Near  the  capsule  they  are 
well  defined  from  one  another,  and  present  a  polygonal 
outline  ;  farther  inwards  they  are  riiore  or  less  fused. 
Each  shows  a  central  transparent  medulla  (germ  centre) 
and   a   peripheral   less  transparent  cortex   (Watney). 


132 


Elements  of  Histology. 


At  tlie  places  where  two  follicles  are  fused  with  one 
another  the  medulla  of  both  is  continuous.  The  matrix 
is  adenoid  reticulum,  the  fibres  of  the  medullary  part 
being  coarser  and  shorter,  those  of  the  cortical  portion 
of  the  follicle  liner  and  longer.  The  meshes  of  the 
adenoid  reticulum  in  the  cortical  part  of  the  follicles 
are  filled  with  lymph  corpuscles  like  those  occurring  in 
the  adenoid  tissue  of  otlier  organs,  but  in  the  medul- 
lary part  they  are  fewer,  and  the  meshes  are  more  or 
less  completely  occupied  by  the  enlarged  but  more 
transparent  cells  :  in  many  of  these  mitotic  division  of 
the  nucleus  occurs.  These  conditions  cause  the  neater 
transparency  of  the  medulla  and  represent  the  germ 
centres  above  mentioned.     Amongst  the  laro-e  cells  of 

the  medullary  portion, 
some  are  coarsely  granu- 
lar and  include  more 
than  one  nucleus ;  some 
are  even  multinucleated 
giant  cells. 

128.  Amongst  the  cells 
of  the  medulla  occur  also 
larger  or  smaller,  more 
or  less  concerTErically  arranged  nucleated  protoplasmic 
ijiasses.  which  are  the  concentric  bodies  of  Hassall 
(Fig.  92).  They  are  met  with  even  in  the  early 
stages  of  the  life  of  the  thymus,  and  cannot  there- 
fore be  connected  with  the  involution  of  the  gland, 
as  maintained  by  Afanassief,  according  to  whom 
the  concentric  corpuscles  are  formed  in  blood-vessels 
which  thereby  become  obliterated.  According  to 
Watney  they  are  concerned  in  the  formation  of  blood- 
vessels and  connective  tissue. 

The  lymphatics  of  the  interfollicular  septa  and 
trabecular  always  contain  numbers  of  lymph  corpuscles. 
The  blood  capillaries  of  the  follicles  are  more  richly 
distributed  in   the  cortex   than  in  the  medulla,   and 


Fig.  92. — Two  Concentric  or  Hassall's 
Corpuscles  of  the  Thymus.  Foetal 
Gland. 


S/MPf-F.   LvMriiAric  Glands.  133 

they  radiate  from  the  periphery  towards  the  central 
parts. 

129.  After  birth  the  thymus  begins  to  undergo 
involution,  leading  to  the  gradual  disappearance  of 
the  greater  portion  of  the  gland,  its  place  l)eing  taken 
by  connective  tissue  and  fat.  But  the  time  when 
the  involution  is  completed  varies  within  very  wide 
limits. 

It  is  not  unusual  to  find  in  persons  of  tifteen  to 
twenty  years  of  age  an  appreciable  amount  of  thymus 
tissue.  According  to  Waldeyer,  about  60  per  cent,  of 
adults  examined  had  still  a  portion  of  thymus  gland 
left.  In  some  animals— e.^.  guinea-i)ig — the  involu- 
tion of  the  gland  even  in  the  adult  has  not  made  much 
progress.  In  the  thymus  of  the  dog  Watney  found 
cysts  lined  with  ciliated  epithelial  cells. 


134 


CHAPTER  XTII. 

COMPOUND    LYMPHATIC    GLAXDS. 

130.  The  compound  or  true  lymphatic  glands  are 
nodules,  generally  of  an  oblong  shape,  directly  inter- 
]>olated  in  the  course  of  lymphatic  vessels.  Such  are 
the  mesenteric,  portal,  bronchial,  splenic,  sternal, 
cervical,  culntal,  popliteal,  inguinal,  lumbar  glands. 
Afferent  lymphatic  vessels  anastomosing  into  a  plexus 
open  at  one  side  (in  the  outer  capsule)  into  the 
lymphatic  gland,  and  at  the  other  (the  hilum)  emerge 
from  it  as  a  plexus  of  efferent  lymphatic  tubes. 

131.  Each  true  lymphatic  gland  is  enveloped  in  a 
fibrous  capsule  which  is  connected  with  the  interior 
and  the  hilum  by  traheculcn  and  septa  of  connective 
tissue.  The  trabeculse  havincj  advanced  a  certain 
distance,  about  one-third  or  one-fourth,  towards  the 
centre,  branch  into  minor  trabecular,  which  in  the 
gland  anastomose  with  one  another  so  as  to  form  a 
plexus  with  small  meshes.  Thus  the  peripheral  third 
or  fourth  of  the  gland  is  subdivided  by  the  septa  and 
trabeculte  into  relatively  large  spherical  or  oblong 
compartments,  while  the  middle  portion  is  made  up  of 
relatively  small  cylindrical  or  irregularly-shaped  com- 
partments (Fig.  93).  The  former  region  is  the  cortex^ 
the  latter  the  meduUa  of  the  gland.  The  compart- 
ments of  the  cortex  anastomose  with  one  another  and 
with  those  of  the  medulla,  and  these  latter  also  form 
one  intercommunicating  system. 

The  fibrous  capsule,  the  septa  and  trabecuhe  are 
tlie  carriers  of  the  vascular  trunks  ;  the  trabeculse 
consist  of  fibrous  connective  tissue  and  of   a  certain 


Compound  Lymphatic  Glands. 


135 


amount  of  non-striped  nuiscular  tissue,  which  is  con- 
spicuous in  some  animals — e.g.  pig,  calf,  rabbit, 
guinea-pig^but  is  scanty  in  man. 

Sometimes  coarsely  granular  connective-tissue  cells 
(plasma  cells)  are  present  in  considerable  numl^ers  in 
the  trabecuhe. 

132.   The  com})artments  contain  masses  of  adenoid 


Fig.  03.— From  a  Vertical  Section  through  a  Lj-mphatie  Gland,  the 
Lymphatics  of  which  had  been  injected.     {Atlas.) 

c,  Outer  capsule,  with  lymphatic  vessels  in  section;  «,  corticallymph  follicles; 
around  them  are  the  cortical  lymph  sinuses;  b,  medulla;  injected  lymph 
sinuses  between  the  masses  of  adenoid  tissue. 

tissue,  without  being  completely  filled  with  it.  Those 
of  the  cortex  contain  oval  or  spherical  masses — the 
lymph  follicles  of  the  cortex  ;  those  of  the  medulla 
cylindrical  or  irregularly-shaped  masses — the  medullary 
cylinders.  The  former  anastomose  with  one  another 
and  with  the  latter,  and  the  latter  amongst  them- 
selves, a  condition  easily  understood  from  what  has 
been  said  above  of  the  nature  of  the  compartments 
containing  these  lymphatic  structures.     The  follicles 


136 


Elements  of  Histology. 


and  medullary  cylinders  consist  of  adenoid  tissue  with 
germ  centres  of  exactl}^  similar  character  to  that 
described  in  the  previous  chapter.  And  this  tissue 
also  contains  the  last  ramifications  of  the  blood- 
vessels— i.e.  the  last  branches  of  the  arteries,  a  rich 
netwoik  of  capillary  blood-vessels,  and  the  first  or 
smaller  branches  of  the  veins.  The  capillaries  and 
other  vessels  receive  also  here  an  adventitious  envelope 
fiom  the  adenoid  reticulum. 

133.    The    cortical    follicles    and    the    medullaiy 

cylinders  do  not 
completely  fill  out 
the  compartments 
made  for  them  by 
the  capsule  and 
trabecular  respec- 
tively, but  a  nar- 
row peripheral 
zone  in  each  com- 
jmrtment  is  left 
free;  these  are  the 
lymphatic  sinuses. 
In  the  cortex  they 
are  spoken  of  as 
the  cortical  (Fig. 
94),  in  the  medulla 
as  the  medullary  J 
lyinj)h  sinuses 

(Fig.     95).       The 
former  is  a  space 
between  the  outer 
surface  of  the  cor- 
tical lymph  follicle 
and      the      corre- 
sponding part  of  the  capsule  or  cortical  septum,  the 
latter   between   the  surface  of   a  medullary  cylinder 
and  the  trabecuhe.      From  what  lias  been  said  of  the 


n 


eT?:^'^^ 


Fi 


04.— Fnnii  a  Section  tlninigli  a  Lyiiiiiliatic 
Gland.     (Atlas.) 

Outer  caisiile;  s,  cortical  lyiiii>li  sinus;  a, 
adenoid  tissue  of  cortical  follicle.  Numerous 
nuclei,  indicating  lynijiL  corpuscles. 


Com  POUND  Lymphatic  Glands. 


137 


relation  of  the  compartments,  it  follows  that  the 
cortical  and  medullary  lymph  sinuses  form  one  inter- 
communicating system.  These  are  not  empty  free 
spaces,  but  are  filled  with  a  coarse  reticulum  of  fibres, 
much  coarser  than  the  adenoid  reticulum  ]  to  it  are 
attached    large    transparent  cell   plates — endotheloid 


Fig.  95. — From  a  Section  Uirough  the  Medulla  of  a  Lymphatic  Gland. 

a,  Transition  of  the  medullary  cylinders  of  adenoid  tissue  into  the  cortical 
follicles;  6,  lymph  sinuses  occupied  by  a  reticulum;  c,  fllirous  tissue  trabe- 
culae  ;  d,  medullary  cylinders. 

plates.  In  some  instances  (as  in  the  calf)  these  cell 
f)lates  of  the  medullary  sinuses  contain  brownish 
pigment  granules,  which  give  to  the  medulla  of  the 
gland  a  dark  brown  aspect.  In  the  meshes  of  the 
reticulum  of  the  sinuses  are  contained  lymph  cor- 
puscles, the  majority  of  which  consist  of  a  compara- 
tively large  protoplasmic  body  and  one  or  two  nuclei ; 


138  Elements  of  Histology. 

they  show  lively  amoeboid  movement ;  a  few  small 
lymphocytes  are  also  amongst  them. 

The  surface  of  the  trabeculse  facing  the  lymph 
sinuses  is  covered  with  a  continuous  layer  of  endothe- 
lium (von  Recklinghausen),  and  a  similar  endothelial 
membrane,  but  not  so  complete,  can  be  made  out  on 
the  surface  of  the  cortical  follicles  and  the  medullary 
cylinders.  The  endotheloid  plates,  applied  to  the 
reticulum  of  the  sinuses,  are  stretched  out,  as  it 
were,  between  the  endothelial  membrane  covering 
the  surface  of  the  trabecular  on  the  one  hand  and 
that  covering  the  surface  of  the  follicles  and  cylinders 
on  the  other. 

In  the  mesenteric  glands  of  the  pig  the  distribu- 
tion of  cortical  follicles  and  medullary  cylinders  is 
almost  the  i-everse  from  that  of  other  glands  and  in 
other  animals  :  the  cortical  part  having  the  arrange- 
ment of  cylinders  of  adenoid  tissue  and  trabeculai, 
while  the  medulla  shows  lymph  follicles  and  longer 
septa  between  them. 

134.  The  afferent  lymphatic  vessels  having  entered 
the  outer  capsule  of  the  gland,  and  having  formed 
within  the  capsule  a  dense  plexus,  open  directly  into 
the  cortical  lymph  sinuses.  The  medullary  lymph 
sinuses,  on  the  other  hand,  lead  into  lymphatic  vessels, 
which  leave  the  gland  at  the  hilum  as  the  efferent 
vessels. 

Both  afferent  and  efferent  vessels  are  supplied 
with  valves. 

135.  The  course  of  the  lymph  through  a  lymphatic 
gland  is  this  :  From  the  afferent  vessels,  situated  in 
the  capsule,  the  lymph  flows  into  the  cortical  lymph 
sinuses,  from  these  into  the  medullary  sinuses,  and 
from  these  into  the  efferent  lymphatics.  Owing  to 
the  presence  of  the  reticulum  in  the  lymph  sinuses  the 
current  of  the  lymph  will  flow  very  slowly  and  with 
difficulty,   as  if  through    a  spongy    Alter.     Hence  a 


Compound  Lympi/atic  Glands.  139 

large  number  of  formed  corpuscles,  pigment,  inflam- 
matory or  other  elements,  passing  into  the  gland  from 
the  afferent  vessels  are  easily  arrested  and  deposited 
in  the  sinuses,  and  are  there  readily  swallowed  by  the 
amre'boid  corpuscles  lying  in  the  meshes  of,  or  de- 
posited on  the  reticulum. 

Passing  a  stream  of  water  by  way  of  the  afferent 
lymph  vessels  through  the  gland,  the  contents  of  the 
meshes  of  the  reticulum  of  the  sinuses — i.e.  the 
lymph  corpuscles  — are  of  course  the  first  things 
washed  out  (von  Recklinghausen),  and  on  continuing 
the  stream  some  of  the  lymph  corpuscles  of  the 
follicles  and  cylinders  are  also  washed  out.  Probably 
also  by  the  normal  lymph-stream  passing  from  the 
minute  arteries  and  capillary  blood-vessels  of  the 
adenoid  tissue  (follicles  and  medullary  lymph 
cylinders)  into  the  lymph  sinuses,  lymph  cells  are 
drained,  as  it  were,  from  the  follicles  and  cylinders 
into  the  sinuses.  The  amoeboid  movement  of  these 
cells  will  greatly  assist  their  passage  into  the  sinuses. 
From  here  the  cells  are  carried  away  by  the  lymph 
current  into  the  efferent  lymph  vessels,  and  are  ulti- 
mately carried  into  the  big  lymph-trunks  discharging 
into  the  big  veins — i.e.  into  the  circulating  blood — as 
white  blood  corpuscles. 


I40 


CHAPTER    XIY. 


NERVE   FIBRES. 


136.  The  nerve  fibres  conduct  impulses  to  or 
from  the  tissues  and  organs  on  the  one  hand,  and  the 
nerve  centres  on  the  other,  and  accordingly  we  have 
to   consider  in  each  nerve  fibre  the    peripheral   and 


Fig.  9(3.— From  a  Transverse  Section  tlirough  the  Sciatic  Nerve  of  Dog. 

ep,  Epineurium  ;  }).  periueuriuni ;  n,  nerve  filires  coustituting  a  nerve  bundle  in 
cross-section  ;  /,  fat  tissue  surroundiug  the  nerve.    {Athig.) 

central  termination  and  the  conducting  part.  The 
latter,  i.e.  the  nerve  fibres  proper,  in  the  cerebro- 
spinal nerves  are  grouped  into  bundles,  and  these 
afifain  into  anatomical  nerve  branches  and  nerve 
Each  anatomical   cerebro-spinal   nerve  con- 


trunks 


Nerve   Fibres.  141 

sists,  therefore,  of  bundles  of  nerve  fibres  (Fig.  96). 
The  general  stroma  b}^  which  these  bundles  are  held 
together  is  fibrous  connective  tissue  called  the  epi- 
neurium  (Key  and  Retzius) ;  this  epineurium  is  the 
carrier  of  the  larger  and  smaller  blood-vessels  with 
which  the  nerve  trunk  is  supplied,  of  a  plexus  of 
lymphatics,  of  groups  of  fat  cells,  and  sometimes  of 
numerous  plasma  cells. 

137.  The  nerve  bundles  or  faiiiculi  (Fig.  97)  vary 
in  size  according  to  the  number  and  size  of  the  nerve 
fibres  they  contain.  They  are  well  defined  by  a 
sheath  of  their  own,  called  perineurium  (Key  and 
Retzius).  This  perineurium  consists  of  bundles  of 
fibrous  connective  tissue  arranged  in  lamella?,  every 
two  lamella?  being  separated  from  one  another  by 
smaller  or  larger  Ijmiph  spaces,  which  form  an  inter- 
communicating system,  and  anastomose  with  the 
lymphatics  of  the  epineurium  wdience  they  can  be 
injected.  Between  the  lamella,  and  in  the  spaces, 
are  situated  flattened  endotheloid  connective-tissue 
corpuscles. 

The  nerve  bundles  are  either  simple  or  compound. 
In  the  former  the  nerve  fibres  are  not  subdivided 
into  groups  within  the  bundle,  in  the  latter  the 
bundles  are  subdivided  by  thicker  and  thinner  septa 
of  fibrous  connective  tissue  connected  with  the  peri- 
neurium. When  a  nerve  bundle  divides  — as  when  a 
trunk  repeatedly  branches,  or  when  it  enters  on  its 
peripheral  distribution — each  branch  of  the  bundle 
receives  a  continuation  of  the  lamellar  perineurium. 
The  more  branches  the  perineurium  has  to  supply, 
the  more  reduced  it  becomes  in  thickness.  In  some 
of  these  minute  branches  the  perineurium  is  reduced 
to  a  single  layer  of  endothelial  cells.  When  one  of 
these  small  bundles  breaks  up  info  single  nerve 
fibres,  or  into  small  groups  of  them,  each  of  these  has 
also    a    continuation    of    the    fibrous    tissue    of    the 


142 


Elemexts  of  Histology. 


perineurium.  In  some  places  this  perineural  con- 
tinuation is  only  a  very  delicate  endothelial  membrane 
as  just  mentioned,  in  others  it  is  of  considerable 
thickness,  and  still  shows  its  lamellated  nature.    Such 


Fig.  07.— Transverse  Section  through  a  Xerve  Bundle  in 
the  Tail  of  Mouse.     i^AtUs.) 

p.  Perineurium ;  c,  endoneurium  separating  the  medullated  nerve  fibres 
seen  in  cross-section ;  i,  lymph  spaces  in  the  perineurium;  i,  lymph  spaces 
in  the  endoneurium. 


a  lamellated  sheath  of  single  nerve  fibres,  or  o  a 
small  group  of  them,  represents  what  is  called  a 
He /lie's  sheath. 

138.  The  nerve  fibresarehekl  together  or  separated 
respectively  within  the  bundle  by  connective  tissue, 
called  the  endoneurium  (Fig.  97 j.  This  is  a  homo- 
geneous crround  substance  in  which  are  embedded 
tine  bundles  of  fibrous  connective  tissue,  and  con- 
nective-tissue corpuscles,  and  capillary  blood-vessels 
arranged  so  as  to  form  a  network  with  elongated 
meshes.  Between  the  perineurium  and  the  nerve 
fibres  are  found  here  and  there  lymph  spaces  ;  similar 
spaces  separate  the  individual  nerve  fibres,  and  have 
been  injected  by  Key  and  Retzius.  The  endoneural 
lymph  spaces  communicate  with  those  of  the  peri- 
neural sheath. 


A^ER  VE  Fibres  .  143 

When  nerve  trunks  anastomose  so  as  to  form  a 
plexus — e.g.  in  the  brachial  or  sacral  plexus — there 
occurs  a  division,  an  exchange  and  re-arrangement 
of  nerve  bundles  in  the  branches.  A  similar  con- 
dition obtains  in  the  ganglia  of  the  cerebro- spinal 
nerves.  Nerve  trunks  and  nerve  branches  passing 
through  a  lymph  cavity,  such  as  the  subdural  spaces, 
or  the  subcutaneous  lymph  sacs,  or  the  cisterna  lym- 
phatica  magna  in  the  frog,  receive  from  the  serous 
membrane  an  outer  endothelial  covering. 

139.  Most  of  the  nerve  fibres  in  the  bundles  of 
the  cerebro-spinal  nerves,  with  the  exception  of  the 
olfactory  nerve,  are  meduUatecl  nerve  fibres.  These 
are  doubly  -  contoured  smooth  cylindrical  fibres, 
varying  in  diameter  between  ttoVo  ^^  more  and 
iToooo  ^^  ^^^  inch.  Within  the  same  nerve,  and 
even  wdthin  the  same  nerve  bundle,  there  occur 
fibres  which  are  several  times  thicker  than  others, 
and  it  is  probable  that  they  are  derived  from  different 
sources  ;  this,  for  instance,  is  very  conspicuous  in  the 
vagus  nerve  (Gaskell,  Fig.  98).  Schwalbe  has  shown 
that  the  thickness  of  the  nerve  fibre  stands  in  a 
certain  relation  to  the  distance  of  its  perijihery  from 
the  nerve  centre  and  to  its  functional  activity. 

A  medullated  nerve  fibre  in  the  fresh  condition  is 
a  bright  glistening  cylinder,  showing  a  dark  double 
contour.  Either  spontaneously  after  death,  or  after 
reagents — as  water,  salt  solution,  dilute  acids — or 
after  pressure  and  mechanical  injury,  the  outline  of 
the  nerve  fibre  becomes  irregular;  smaller  or  larger 
glistening  dark-bordered  droplets  and  masses  appear, 
and  gradually  become  detached.  These  droplets  and 
masses  are  called  myeline  droplets^  and  are  derived 
from  the  fatty  substance  or  myelin  constituting  the 
medullary  sheath  or  white  substance  of  Schwann  (see 
below).  When  a  nerve  fibre  within  the  bundle  under- 
goes degeneration  during  life,  either  after  section  of 


144 


Elemexts  of  Histology. 


the  ner\'e  or  after  other  pathological  changes,  or  in 
the  natural  course  of  its  existence  (S.  Maver),  the 
medullarv  sheath  is  the  first  to  undergo  cliange  ;  it 
breaks  uj)  into  similar  smaller  or  larger  globules  or 


Fig.  98. — From  a  Transverse  Section  through  the  Vagus  Xerve,  showing  in 
the  nerve  bundles  nerve  fibres  (in  cross-section)  which  differ  markedly 
in  size,  some  being  much  larger  than  others.    (Photo.,  highly  imignified.) 


particle-,  whicli  gradually  l)ec'ome  granular  and 
absorbed.  Later  also  the  axis  cylinder  dwindles 
away,  and  only  the  neurilemma  with  the  nucleated 
corpuscles  persist. 

140.  Each  medullated  nerve  fibre  (Figs.  99,  101) 
consists  of  tlie  following  parts  :  {a)  the  central  axis 
cylinder,  axon  or  neuraD:on.  This  is  the  essential 
part   of   the  fibre,   and    is  a   cylindrical  or  band-like. 


Nerve  Fibres.  145 

pale,  trans|>ureiit  structure,  which  in  certain  locali- 
ties (near  the  terminal  distribiiiion,  in  tlie  olfactory 
nerves,  in  the  centj'al  nervous  system),  and  especially 
after  certain  reagents,  shows  itself  composed  of  very 
fine  homogeneous  or  more  or  less  beaded  tibrilhe — the 
elementary  or  jjriniitive  Jibrillfe  (Max  Schultze) — held 
together  by  a  small  amount  of  a  faintly  gianular  in- 
terstitial substance  The  longitudinal  striation  of 
the  axis  cylinder  is  due  to  its  being  composed  of 
primitive  librillcV.  The  thickness  of  the  axis  C3dinder 
is  in  direct  proportion  to  the  thickness  of  the  whole 
nerve  tibre.  The  axis  cylinder  itself  is  enveloped  in 
its  own  hyaline  more  or  less  elastic  sheath — the  axi- 
lemma  (Kiihne),  composed  of  neurokeratin. 

1-1:1.  (b)  The  medidlarij  sheath,  or  myeline  sheath, 
or  white  substance  of  Schwann,  is  also  called  the 
medulla  of  the  nerve  fibre.  This  is  a  olisteninff 
bright  fatty  substance  surrounding  the  axis  cylinder, 
as  an  insulating  hollow  cylinder  surrounds  an  electric 
wire.  The  medullary  sheath  gives  to  the  nerve  fibre 
its  double  or  dark  contour.  Between  the  axis  cylinder 
and  the  medullary  sheath  there  is  a  small  amount  of 
albuminous  fluid,  which  appears  greatly  increased 
when  the  former,  owing  to  shrinking,  stands  farther 
apart  from  the  latter. 

142.  (c)  The  sheath  of  Scliicann,  or  the  neurileinma, 
closely  surrounds  the  medullary  sheath,  and  forms  the 
outer  boundary  of  the  nerve  fibre.  It  is  a  delicate 
structureless  membiane.  Here  and  there  between 
the  neurilemma  and  the  medullary  sheath,  and 
situated  in  a  depression  of  the  latter,  is  an  oblong- 
nucleus,  surrounded  by  a  thin  zone  of  protoplasm. 
These  nucleated  corpuscles  are  the  nerve  corpuscles 
(Fig.  99),  and  are  analogous  to  the  muscle  corpuscles, 
situated  between  the  sarcolemma  and  the  striated 
muscular  substance.  They  are  not  nearly  so  numerous 
as  the  muscle  corpuscles. 
K 


146 


Eleisients  of  Histology 


143.  The  neurilemma  presents  at  certain  definite 
intervals  annular  constrictions — the  nodes  or  constric- 
tions  of  Rani-ier  (Figs     99,    100,  101) — and  at  these 

nodes  of  Ranvier  the  medullary 
sheath,  but  not  the  axis  cylinder  and 
its  special  sheath,  is  suddenly  inter- 
rupted, and  sharply  terminates  at 
the  constriction.  The  neurilemma 
is  at  the  same  time  thickened  by 
annular  permanent,  folds  (see  b  in 
Fig.  101).  The  portion  of  the  nerve 
fibre  situated  between  two  nodes  is 
the  internodal  segment.  Each  in- 
ternodal  seojment  has  orenerallv  one, 
occasionally  more  than  one,  nerve 
corpuscle.  The  medullary  cylinder 
of  each  internodal  segment  is  made 
up  of  a  number  of  conical  sections 
(Fio-.  101,  A)  imbricated  at  their  ends 

¥W  99.  -Two  Nerve       -    ^      . 

Fibre's,  showing  the    (Schmidt,     Lantermann ;     and     each 

such  section  is  again  made    uj)    of  a 

large  number   of    rod-like  structures 

(Fig.    102)   placed   vertically   on   the 

been       dissolved    axis    cvlinder     (MacCarthy). 
away.  The  deeply-  „    -  ,    ^  1 

ihese  rods  are,  however,  con- 
nected into  a  network.  The  net- 
work itself  is  verv  likelv  the  neuro- 
keratin  of  Ewald  and  Kiihne,  where- 
as the  interstitial  substance  of  the  network  is 
probably  the  fatty  substance  leaving  the  nerve 
fibre  in  the  shape  of  myeline  droplets,  when  pres- 
sure or  reagents  are  applied  to  the  fresh  nerve 
fibre. 

144.  Medullated  nerve  fibres  without  any  neuri- 
lemma, and  consequently  without  any  nodes  of 
Ranvier,  with  a  thick  more  or  less  distinctly  laminated 
medullary  sheath,  form  the  entire  white  substance  of 


nodes  or  constric 
tions  of  Ranvier 
and  the  axis  cy- 
linder. The  me- 
dullary sheath  has 


stained  oblong 
nuclei  indicate  the 
ner\'e  corpuscles 
within  the  neuri- 
lemma.    (Atlas.) 


Ner I'E   Fibres. 


147 


the  brain  and  spinal  cord.  In  these  organs,  in  the 
hardened  and  fresh  state,  numerous  nerve  fibres  may 
be  noticed,  whicli  show 

more    or    less    regular  f(iil//'i///(' l|-i  N^I/f^PI 

varicosities,    owing   to  ((allllamlmru  il/^^  h 

local  accumulations  of  /:  M lUlnf/rnwi !Wm% 

fluid  between  the  axis  /J l////tl W^lJ ///j  > ^^^^ 

cylinder  and  medullary  jl  B ni f'lJ'/^^iJf'liHwV^ 

sheath.         These     are 
called    varicose    nerve 


B         \\\l^ 


Fig.    101.— Medullated     Xerve 
Fibres. 

A,  Medullated  nerve  fibre,  show- 
ing the  subdivision  of  tlie 
medullary  sheath  into  cylin- 
drical sections  imbricated  with 
their  ends  ;  a  nerve  corpuscle 
with  an  oval  nucleus  is  seen 
between  tlie  neurilemma  and 
the  medullary  sheath,  b,  me- 
dullated nerve  fibre  at  a  node 
or  constriction  of  Kanvier  ;  the 
axis  cylinder  passes  uninter- 
ruptedly from  one  se.L'inent 
into  the  other,  but  the  medull- 
ary s  sheath  is  interrupted. 
(Key. and  Retzius.) 


Fig.  100.— Medullated  Xerve  Fibies,  after 
staining  with  nitrate  of  silver.  {Key 
and  Retzius.) 

rt.  Axis  cylinder;  h,  Ranvier's  constriction. 

fibres.  They  occur  also  in 
the  branches  of  the  sympa- 
thetic nerve. 

The  nerve  fibres  of  the 
optic  and  acoustic  nerve  are 
medullated,  but  without  any 
neurilemma  ;  they  are  there- 
fore without  any  nodes  of 
Ranvier.  Varicose  fibres  are 
common  in  them. 

145.  Medullated  nerve 
fibres  occasionally  in  their 
course  divide  into  two  me- 
dullated fibres.  Such  divi- 
sion    is     very     common     in 


148 


Elements  of  Histology. 


medullated  nerve  libres  supplying  striped  muscular 
tissue,  especially  at  or  near  the  point  of  entrance 
into  the  muscular  fibres.  (See  below.)  But  also 
in  other  localities  division  of  nerve  fibres  may  be 
met   witli.      Tlie   electric  nerve  of    the  electric  fishes 

—  e.g.  malapterurus,  gym- 
notus,  silurus — shows  such 
divisions  to  an  extraor- 
dinary degree,  one  huge 
nerve  fibre  dividinc;  at 
once  into  a  bundle  of 
minute  fibres.  Division 
of  a  medullated  fibre 
takes  place  generally  at 
a  node  of  Ranvier.  The 
branches  taken  together 
are  generally  thicker  than 
the  undivided  part  of  the 
fibre,  but  in  structure 
they  are  identical  with 
the  latter. 

146.      When     medul- 
lated    nerve     fibres     ap- 
proach    their    peripheral 
Medullated  xen-e  Fibres,    termination,  they  change 

A,  B.  Showinc  on    a  surface  view  the  i    x  •  1 

reticulated  nature  of  the  medullary  SOOner    Or  later,   inasmUCh 
sheath;  c,  two  nerve  fibres  showintr  ±a     •  in  1        ji 

the    axis    cylinder,    the    medullary  aS  their  meOUJlary  Slieath 
sheath  with  their  vertically-arranged  i  i       i  i 

minute  rods,  and  the  delicate  neuri-  SUCluenlV  CeaSCS  ;  and  UOW 
lemma     or    outer    hyaline    sheath.  i       '  77 

{.Atlas.)  Ave     have     a     non-meam- 

lated  or  grey  (trans- 
parent) nerve  fibre  of  Remak.  Each  of  these  consists 
of  an  axis  cylinder,  a  neurilemma,  and  between  the 
two  a  nucleated  nerve  corpuscle  from  place  to  place. 
Xon-medullated  nerve  fibres  alwavs  show  the  fibrillar 
nature  of  their  axis  cylinder.  The  olfactory  nerve 
branches  are  entirely  made  up  of  non-meduUated 
nerve  fibres.      In    the    branches    of  the   sympathetic 


A^ER  I  'E   Fibres. 


149 


most  tilnes  arc  iiou-medullated.  Non-medullated 
til)res  do  not  show  Raiivier's  constrictions.  Bundles  of 
non-medullated  fibres  are  grey,  bundles  of  medullated 
Hbres  are  white,  when  viewed  in  reflected  light ;  the 
former  being  without  medullary  sheath  allo'.v  light  to 


Fig.  103. — View  of  the  anterior  surface  of  Gold-stained  Cornea  of  Guinea- 
pig,  showing  the  rich  distribution  of  the  terminal  nerve  tibrilhe  and 
their  ramifications  in  the  anterior  epithelium  of  the  cornea.  {Photo., 
highly  magnified.) 


pass  through    them,   while   the  latter   owing  to  their 
medullary  (fatt}')  sheath  reflect  light  strongly. 

In  the  extra-vertebral  course  of  many  branches 
of  the  cerebro-spinal  nerves — e.g.  those  supplying  the 
limbs,  the  wall  of  the  chest  and  abdomen — there  occur 
non-medullated    fibres    generally    in    small    groups ; 


ISO 


Elements  of  Histology. 


these  fibres  are  considered  to  be  derived  from  the 
sympathetic  system,  haviiii;'  joined  the  cerebro  spinal 
nerves  by  the  grey  portions  of  the  rami  communi- 
cantes  (Gaskell).  Tiie  non  medullated  fibres  near  their 
terminal  distribution  always  undergo  repeated  divi- 
sions. They  form  plexuses,  large  fibres  branching 
into  smaller  ones,  and  these  again  joining.      Gener- 


Fig.  104. — Dendritic  terminations— Demlrons  of  Xerve  Fibres.  Transverse 
section  of  the  optic  lobe  of  a  binl  prepared  by  Golgi's  method.  (R.  y 
Cajal.  from  Quain.) 

a,  Optic  fibres;  ft,  c,  rf,  e,  dendrons  of  same  in  the  diifereiit  layers  of  the  optic 
lobe  ;  6  and  7  are  the  sixth  and  .seventh  layers  respectively  of  the  organ. 


ally  at  the  nodal  points  of  these  plexuses  there  are 
triangular  nuclei,  indicating  the  corpuscles  of  the 
neurilemma. 

147.  Finally  the  non-medullated  nerve  fibres  leav- 
ing tlie  plexuses  ultimately  lose  their  neurilemma  and 
l)reak  up  into  tlieir  constituent  small  bundles  and 
even  single  primitive  nerve  fihrillce,  which  occasion- 
ally show  regular  varicosities  (Fig.  105).  Of  course, 
of  a  neurilemma  or  the  nuclei  of  the  nerve  corpuscles 
there  is  nothing  left.      The  bundles  of  primitive  fibrils 


Nerve   Fibres. 


T51 


and  also  single  fibrils  branch  and  interlace,  whereby  a 
more  or  less  dense  dendritic  ramification — avhoriHa- 
tion  or  (/c?irfywi— is  produced  (Fig.  104).     The  indivi- 


Fig.  105. — Nerve  Fibres  of  tlie  Cornea. 

a,  Axis  cylinder  near  the  anterior  epithelium  of  the  cornea  splitting  up  into 
its  constituent  primitive  flbrillaj ;  &,  primitive  flbrillae. 


dual  fibrils  of  the  dendron  are  straight  or  twisted,  and 
often  provided  with  smaller  or  larger  terminal  knobs. 
In  some  localities — e.g.  in  the  grey  matter  of  the 
central    nervous  system — the  number   of  fibrils  con- 


152 


Elements  of  Histology. 


stituting  a  dendron  is  large,  and  hence  the  dendron 
is  conspicuous,  in  other  localities  the  number  of  tibrils 
is  relatively  scanty — e.g.  in  the  anterior  epithelium 
of  the  cornea — and  hence  the  arborising  character 
of   the  dendron  is  not  very  conspicuous  (Fig.    103). 


Fig.  106. — Intra-epitlielialXerve-teriniuation  in  the  Anterior  Epithelium  of 
the  Cornea,  as  seen  in  an  oblique  section.     (Handbook.) 

a.  Axis  cylindei' ;  b,  sub-epithelial  nerve  flbrillie ;  c,  iutra-epithelial  i-amiflcatiou  ; 
d,  epithelial  cells. 


Pronounced  dendrons  are  found  in  the  nerve  termin- 
ation in  muscle  and  tendon  (the  endplates)  in  the 
branched  processes  (dendrites)  of  the  ganglion  cells 
in  the  central  nervous  system,  as  will  be  described 
and  illustrated  later. 

In  the  skin,  cornea  and  mucous  membranes, 
the  peripheral  termination  — ■  i.e.  the  primitive 
fibrils  and  their  ramitications.  are  intra-epithelial 
(Fig.  lOG),  i.e.  they  are  situated  in  the  stratum 
Malpighii  of  the  epidermis,  in  the  epithelial  parts  of 


NeR  VE     FlBR  ES. 


153 


the  hair  follicle,  in  the  anterior  epithelium  of  the 
cornea,  or  in  the  epithelium  of  the  mucous  mem- 
branes. The  primitive  nerve  fibrils  lie  in  the  inter- 
stitial substance  between  the  epithelial  cells,  and  some 
of   them    have    been    observed    to    end   with  minute 


Fig.  107. — From  gold-stained  cornea  of  frog,  showing  the  numerous  beaded 
line  nerve  fibrils  and  the  branched  corneal  corpuscles.  [Photo.,  highly 
magnified.) 


knobs    in    the    cell    substance    itself    close     to    the 
nucleus  (Pfitzner,  Macallum). 

148.  Tracing  then  a  nerve  fibre,  say  one  of  com- 
mon sensation,  from  the  periphery  towards  the  centre, 
we  have  isolated  primitive  fibrils  or  their  ramifications  ; 
they  form  by  aggregation  simple  axis  cylinders,  which 
vary  in  thickness  according  to  the  number  of  their 


154  Elemexts  of  Histology. 

constituent  primitive  til)rils.  These  axis  cylinders 
then  become  invested  bv  neurilemma  and  nuclei,  and 
form  plexuses.  By  association  they  form  larger  axis 
cylinders,  and  these  form  typical  non-medullated  nerve 
fibres  with  neurilemma,  and  with  the  nuclei  of  nerve 
corpuscles  (Fig.  106).  Lastly,  if  a  medullary  sheath 
makes  its  appearance  between  the  neurilemma  and 
the  axis  cylinder  of  each  fibre  we  get  a  rneduUated 
nerve  fibre. 


155 


CHAPTER    XV. 

PERIPHERAL    NERVE-ENDINGS. 

149.  In  the  preceding  chapter  we  referred  to  the 
termination  of  the  nerves  of  common  sensation,  .as  iso- 
lated primitive  fibrillre,  and  as  ramifications  and  den- 
drons  of  these  in  the  epitlielium  of  the  skin  and  mucous 
membranes,  in  the  anterior  epithelium  of  the  cornea, 
and  in  the  grey  matter  of  the  central  nervous  system. 
Besides  these  there  are  other  special  terminal  organs 
of  sensory  nerves,  probably  concerned  in  the  per- 
ception of  some  special  quality  or  quantity  of  sensory 
impulses.  These  are  all  connected  with  a  meduUated 
nerve  fibre,  and  are  situated  not  in  the  epithelium 
of  the  surface  but  in  the  tissue,  at  greater  or  lesser 
depth.  Such  are  the  corpuscles  of  Pacini  and  Herbst, 
the  end-bulbs  of  Krause  in  the  tongue  and  con- 
junctiva, the  genital  end-corpuscles  or  end-bulbs  in 
the  external  genital  organs,  the  corpuscles  of  Meiss- 
ner  or  tactile  corpuscles,  in  the  papillae  of  the  skin 
of  the  volar  side  of  the  fingers,  the  touch-cells  of 
Merkel,  the  end-corpuscles  of  Grandry,  in  the  beak 
and  tongue  of  the  duck. 

150.  The  Paciiiisiii  corpuscles. — These  are 
also  called  Yater's  corpuscles.  They  occur  in  large 
numbers  on  the  subcutaneous  nerve  fibres  of  the  jDalm 
of  the  hand  and  foot  of  man,  in  the  mesentery  of  the 
cat,  along  the  tibia  of  the  rabbit,  in  the  genital  organs 
of  man  (corpora  cavernosa,  prostate).  Each  corpuscle 
is  oval,  more  or  less  pointed,  and  in  some  places 
(palm  of  the  human  hand,  meseutery  of  the  cat) 
easily   percej)tible    to    the    unaided    eye,    the   largest 


'56 


Elemexts  of  Histology. 


beino;  about  T.^rrtli  of  an  incli  Ioiijt;  and  ^th  of  an 
inch  broad  ;  in  other  places  they  are  of  microscopic 
size.  Each  possesses  a  stalk,  to  which  it  is  attached, 
and  which  consists  of  a  single  medullated  nerve  fibre 
(Fig.    108),    differing    froin    an    ordinary   medullated 

nerve  fibre  merely  in  the 
fact  that  outside  its  neuri- 
lemma there  is  present  a 
thick  laminated  connec- 
tive-tissue sheath.  This 
is  the  sheath  of  Henle 
— continuous  with  the 
perineural  sheath  of  the 
nerve  branch  with  which 
the  nerve  fibre  is  in  con- 
nection. This  medullated 
nerve  tibre  within  its 
sheath  possesses  generally 
a  very  wavy  outline.  The 
corpuscle  itself  is  com- 
posed of  a  large  number 
of  lamella,  or  capsules, 
more  or  less  concentric- 
ally arranged  around  a 
central  elongated  or  cylin- 
drical clear  space.  This 
space  contains  in  its  axis, 
from  the  proximal  end — 
i.e.  the  one  nearest  to  the  stalk — to  near  the  opposite 
or  distal  end,  a  continuation  of  the  nerve  tibre  in  the 
shape  of  a  simple  axis  cylinder.  But  this  axis  cylinder 
does  not  fill  out  the  central  space,  since  there  is 
all  round  it  a  space  left  filled  with  a  transparent 
substance,  in  which,  in  some  instances,  rows  of 
spherical  nuclei  may  be  perceived  along  the  margin 
of  the  axis  cylinder.  At  or  near  the  distal  end  of  the 
central    space    the    axis   cylinder    divides    in   tico   or 


Fig.  lOS. — Pacinian  Corpuscle,  from 
the  Mesentery  of  Cat. 

a,  Medullated  nerve  fibre :  b.  concen- 
tric capsules. 


Per  ipher  a  l  Ner  ve-endings. 


^57 


more  branches,  and  these  terminate  in  pear-shaped, 
oblong,  spherical,  or  irregularly-shaped  granular- 
looking  enlargenients. 

151.  The  concentric  cajjsules  forming  the  corpuscle 
itself  are  disposed  in  a  different  manner  at  the  peri- 
phery and   near  the  central  space 

from  that  in  which  they  are  dis- 
posed in  the  middle  parts,  in  the 
former  localities  being  much  closer 
together  and  thinner  than  in  the 
latter.  On  looking,  therefoi-e,  at 
a  Pacinian  corpuscle  in  its  longi- 
tudinal axis,  or  in  cross-section, 
we  alwaj^s  notice  the  striation 
(indicating  the  capsules)  to  be 
closer  in  the  former  than  in  the 
latter  places.  Each  capsule  con- 
sists of — (rt)  a  hyaline,  probably 
elastic,  ground  substance,  in  which 
are  embedded  here  and  there  (b) 
fine  bundles  of  connective- tissiie 
fibres;  (c)  on  the  inner  surface 
of  each  capsule,  i.e.  the  one 
directed  to  the  central  axis  of  the 
Pacinian  corpuscle,  is  a  single 
layer  of  nucleated  endotJielifd plates. 
The  oblong  nuclei  A'isible  on  the 
capsules  at  ordinary  inspection  are  "•  ^'"^''" u\;^a\vay.'''^  ^''''^ 
the  nuclei  of  these  endothelial 
plates.  There  is  no  fluid  between  the  capsules,  but 
these  are  in  contact  with  one  another  (Huxley). 
Neighbouring  capsules  are  occasionally  connected 
with  one  another  by  thin  fibres. 

152.  In  order  to  reach  the  central  space  of  the 
corpuscle,  the  medullated  nerve  fibre  has  to  perforate 
the  capsules  at  one  pole  ;  thus  a  canal  is  formed 
in  which  is  situated  the  medullated  nervQ  fibre,  and 


Fig.  109.— Herbst's  Cor- 
puscle, from  the 
Tongue    of   Duck. 


1:^8 


Elements  of  Histology. 


as  such,  and  in  a  very  wavy  condition,  it  reaches  the 
proximal  end  of  the  central  space.  This  part  of  the 
nerve  fibre  may  be  called  the  intermediate  part.  The 
lamellae  of  the  sheath  of  Henle  pass  directly  into  the 
peripheral  capsules  of  the  corpuscle. 

Immediately  before  entering  the  central  space, 
the  nerve  fibre  divests  itself  of  all  pirts  except  the 
axis  cylinder,  which,  as  stated  above,  passes  into 
the  central  space  of  the  Pacinian  corpuscle.  In  some 
cases  a  minute  artery  enters  the  corpuscle  at  the 
pole,  opposite  to  the  nerve  fibre ;  it  penetrates  the 
peripheral  capsules,  and  supplies  them  with  a  few 
capillary  vessels. 

loo!^  The  corpuscles  of  Horbst  are  similar  to 
the  Pacinian  corpuscles,  with  this  difference,  that  they 
are  smaller  and  more  elongated,  that  the  axis  cylinder 
of  the  central  space  is  bordered  by 
a  continuous  row  of  nuclei,  and 
tliat  the  capsules  are  thinner  and 
more  closely  placed  (Fig.  109). 
This  applies  especially  to  those  near 
the  central  space,  and  here  between 
these  central  capsules  we  miss  the 
nuclei  indicatinii  the  endothelial 
plates.  Such  is  the  nature  of 
Herbst's  corpuscles  in  the  mucous 
membrane  of  the  tongue  of  the 
duck,  and  to  a  certain  degree  also 
in  tliose  of  the  rabbit,  and  in  ten- 
dons. 

154.  The  tactile  corpuscles, 
or  corpuscles  of  ^leissuer,  oc- 
cur in  the  }>apilhe  of  the  corium  of 
the  volar  side  of  the  fingers  and  toes 
apes  ;  they   are    oblong,   straight,   or 
In  man  they  are  about  —t,  to 


Fig.  IIO'.— Tactile  Cor- 
puscle of  Meiss- 
ner  from  the  Skin 
of  the  Human 
Hand.  (£.  FiscUr 
awl  W.  Flemming.) 

Showing  the  convolu- 
tions of  the  nerve 
fibre. 


in    man  and  in 
slightly  folded. 


1 

3  0  0 


pf  an  inch  long,  and 


5  00 


to 


-i-  of 

2  0  0      ^^ 


an  inch  broad. 


Per  ip/fER  A  L  Ner  ve-endings. 


159 


They  are  connected  with  a  medullated  nerve  fibre — 
generally  one,  occasionally,  V)ut  rarely,  two — with  a 
sheath  of  Henle,  The  nerve  fibre  enters  the  corpuscle, 
but  usually  before  doing  so  it  winds  lound  the  cor- 
puscle as  a  medullated  fibre  once  or  twice  or  oftener, 
and  its  Henle's  sheath  becomes  fused  with  the  fibrous 
capsule  or  sheath  of  the  tactile  corpuscle.  The  nerve 
fibre  ultimately  loses  its  medullary  sheath  and  pene- 
trates into  the  interior  of  the  corpuscle,  where  the  axis 
cylinder  branches ; 
its  branches  retain 
a  coiled  course  all 
along  the  tactile  cor- 
puscle (Fig.  110), 
anastomose  with  one 
another,  and  ter- 
minate in  slight  en- 
largements, pear- 
shaped  or  cylindrical. 
These  enlargements, 
according  to  ]Merkel, 
are  touch-cells.  The 
matrix,  or  main  part 
of  the  tactile  cor- 
puscle consists,  be- 
sides the  fibrous 
sheath  with  nuclei 
and  numerous  elastic 

fibres,  of  fine  bundles  of  connective  tissue,  and 
number  of  nucleated  small  cf-lls. 

155.  The  end-bulbs  of  Krauze. — These  occur 
in  the  conjunctiva  of  the  calf  and  of  man,  and  are 
oblong  or  cylindrical  minute  corpuscles  situated  in 
the  deeper  layers  of  the  conjunctiva,  near  the  corneal 
margin.  A  medullated  nerve  fibre,  with  Henle's 
sheath,  enters  the  corpuscle  (Fig.  111).  This  possesses 
a  nucleated  capsule,  and  is  a  more  or  less  laminated 


Fig.  111. — End-bulljof  Kraii.sc. 

Medullated  nerve  fibre :    b,  caiisule 
corpuscle. 


)f  the 


of  a 


i6o 


Elemexts  of  Histology. 


(in  man  more  granuLir-looking)  structure,  numerous 
nuclei  being  scattered  between  the  lamina?.  Of  the 
nerve  fibre,  as  a  rule,  only  the  axis  cylinder  is  pro- 
longed into  the  interior  of  the  corpuscle.  Occasion- 
ally the  medullated  nerve  fibre  passes,  as  such,  into 
the  corpuscle,  being  at  the  same  time  more  or  less 
convoluted.  Having  passed  to  near  the  distal  ex- 
tremity, it  l)ranches,  and  terminates  with  small 
enlargements  (Krause,  Longworth,  Merkel,  Key  and 
Retzius). 

The  end-hidbs  in  the  genital  organs,  or  the  genital 
corpuscles  of  Krause,  are  similar  in  structure  to  the 
simple  end-bulbs.  They  occur  in  the  tissue  of  the 
cutis  and  mucous  membrane  of  the  penis,  clitoris,  and 
vagina. 

156,  The  €ori>ii«irIe«»  of  Graiidry,  or  tou.ch 
corpuscles  of  Merkel,  in  the  tissue  of  the  papill?e  in 
the  beak  and  tongue  of  birds,  are  oval  or  spherical 
corpuscles  of  minute  size,  possessed  of  a  very  delicate 
nucleated  membrane  as  a  capstile.  aud  consisting  of  a 
series  (two,  three,  four,  or  more;  of  large,  slightly- 
flattened,  granular-looking,  transparent  cells,  each 
with  a  spherical  nucleus,  and  arranged  in  a  vertical 


71       A  B        -^  C 

Fig.  112. — Corpuscles  of  Grandry  in  the  Tongue  of  Duck,     {Iz2uierdo.) 

A,  Composed  of  three  cells :  b.  composed  of  two  cells ;  c,  showing-  the  develop- 
ment of  a  Grandry's  corpuscle  from.tlie  epithelium  covering  the  papilla,  p; 
e,  epithelinra  ;  'i,  nerve  fibre. 

row  (Fig.  112).      A  medullated  nerve  fibre  enters  the 
corpuscle    from    one    side,  and    losing  its   medullary 


Per  ipheral  Ner  ve-endings. 


i6[ 


sheatl),  the  axis  cylinder  brandies,  and  its  branchlets 
terminate,  according  to  some  (Merkel,  Henle),  in  the 
cells  of  the  corpuscle  (touch  cells  of  Merkel)  ;  accord- 
ing to  others  (Key  and  Retzius,  Ranvier,  Hesse, 
Izquierdo),  in  the  transparent  substance  between  the 
touch  cells,  thus  forming  the  '•  disc  tactil  "  of  Ranvier 
or  the  "  Tastplatte  "  of  Hesse.  Neither  theory  seems 
to  us  to  answer  to  the  facts  of  the  case,  since  we  find 


Fig.  113.— Bundles  of  Non-striped  Musenlar  Tissue  surrounded  by 
Plexuses  of  Fine  Xerve  Fibres.     (Hamlbook.) 


that  the  branchlets  of  the  axis  cylinder  terminate, 
not  in  the  touch  cells,  nor  as  the  disc  tactil,  but  with 
minute  swellings  in  the  interstitial  substance  between 
the  touch  cells,  in  a  manner  very  similar  to  what  is 
the  case  in  the  conjunctival  end-bulbs.  According  to 
IMerkel,  single  or  small  groups  of  touch  cells  occur  in 
the  tissue  of  the  papilhe,  and  also  in  the  epithelium, 
in  the  skin  of  man  and  mammals. 

157.  In  Jirtieiilatioiis — e  rj.  the  knee-joint  of 
the  rabbit  —  Xicoladoni  described  numerous  nerve 
branches,  from  which  fine  nerve  fibres  are  given  off. 
Some  of  these  terminate  in  a  network,  others  on 
blood-vessels,  and  a  third  group  enter  Pacinian  cor- 
puscles.   Krause  described  in  the  synovial  membranes 

L 


l62 


Elements  of  Histology 


of  the  joints  of  the  human  fingers  medullated  nerve 
fibres  whicli  end  in  peculiar  tactile  corpuscles,  called 
by  him  '^  articular  nerve  corjiuscles.'" 

158.  The  nerve  branches  snpplyiiig^  non- 
striped  ninsenlar  tissue  are  derived  from  the 
sympathetic  system.  They  are  composed  of  non- 
medullated   fibres,    and    the    branches    are    invested 

in  an  endothelial 

c  5  sheath   (perineu- 

^\"^     \  \\  \  »  rium).  The 

branches  divide 
into  single  or 
small  groups  of 
axis  cylinders, 
which  reunite 
into  a  plexus — 
the  ground 
plexus  of  Ar- 
nold. Small 
fibres  coming  oflf 
from  the  plexus 
supply  the  in- 
dividual bundles 
of  non  -  striped 
muscle  cells,  and 
they  form  a 
plexus  called 
the  intermediary 
lilexus  (Fig. 
113).  The  fibres 
joining  this  plexus  are  smaller  or  larger  bundles 
of  primitive  filu'illa? ;  in  the  nodes  or  the  points 
of  meeting  of  these  fibres  are  found  angular  nuclei. 
From  the  intermediate  plexus  pass  oft'  isolated  or 
small  groups  of  primitive  fibrillar,  which  pursue 
their  course  in  the  interstitial  substance  between 
the    muscle    cells;     these    are     the     intermuscular 


Fig.  114. — Termination  of  Nerves  in  Xon-striped 
Muscular  Tissue.     {Atlas.) 

a,  3Cou-inPduUated  flltre  of  the  iutermediary  plexus; 
b,  fine  intermuscular  flbrils ;  c,  nuclei"  of  mus- 
cul;ir  cells. 


Peri p HER  a  l  Ner  i  'e-end/xgs. 


163 


According  to  Frankenliaiiser 


and 
the 
the 
the 


fibrils  (Fig.  lU) 

Arnold,  tlicy  give  oti'  tiner  tihrils,  ending  in 
nucleus  (or  nucleolus).  According  to  Elischer, 
primitive  fibrils  terminate  on  the  surface  of 
nucleus  with  a  minute  swellinij. 

In  many  localities  there  are  isolated  ganglion  cells 
in  connection  with  the  intermuscular  tibres. 

159.  The  nerves  of  blood-vessels  are  derived 
from  the  sympathetic,  and  they  terminate  in  arteries 
and  veins  in  essentially  the  same  way  as  in  non- 
striped  muscular  tissue,  being  chiefly  present  in  those 


Fig.  115. — Plexus  of  Fine  Xon-iiiedullated  Xerve  Fibres  .surrounding 
Capillary  Arteries  in  the  Tongue  of  Frog,  after  staining  Avith  chloride 
of  gold.     (Handbook.) 

a,  Blood-Tessel ;  6,  connective  tissue  corpuscles ;  c,  thick  non-medullated  fibres 
rf,  plexus  of  fine  nerve  fibres. 


parts  (media)  which  contain  the  non-striped  muscular 
tissue.  But  there  are  also  fine  non-medullated  nerve 
fibres,  which  accompany  capillary  vessels — capillary 
arteries  and  capillary  veins — and  in  some  places  they 
give  off  elementary  fibrils,  which  form  a  plexus 
around  the  vessel  (Fig.  llo).      In  some  localities  the 


1 64 


Elements  of  Histology. 


vascular    nerve    brandies    are    provided    witli     small 
groups  of  ganglion  cells. 

160,   In  striped  muscle  of  man  and  mammals, 
reptiles  and   insects,  the  termination  of  nerve  fibres 


•^^^mfi'ID^-i^i-'K 


•^•^>^' 


4 


Fig.  116. — Nerve-endings  in  Striped  Muscular  Fibres.    (Kindly  lint  by 
Professor  Kiiline.) 
A,  In  fresh  muscular  fibre  of  Lacerta,  x  ^^ ;  b,  in  gold-stained  muscular  fibre 
of   lacerta,    X  ^^•,    c,   in    gold-stained   muscular   fibre    of  flog,   x    ^-Y-  ! 
m,  medullated  nerve  fibre ;  t,  termination  of  axis  cylinder  underneath  the 
sarcolemma  of  the  muscular  flv>re. 

takes  place,  according  to  the  commonly  accepted  view 
of  Iviihne,  in  the  following  manner  (Fig.  116)  : — A 
medullated  nerve  fibre,  enclosed  within  a  lamellated 
sheath  (Henle's  sheath)  divides  at  a  node  of  Ranvier, 
each  branch — a  medullated  nerve  fibre — enters  under  a 
variable  angle  a  striped  muscular  fibre,  the  neurilemma 


Periphera  l  Ner  ve-endings. 

becoming  fused  with  the 
sarcolemuia,  and  the  nerve 
fibre,  either  at  tlie  point 
of  entrance  or  immediately 
afterwards,  loses  its  medul- 
lary sheath,  so  that  only  the 
axis  cylinder,  with  its  axi- 
lemma,  })asses  on,  and  then 
forms  on  the  sui'face  of  the 
muscular  substance  a  ter- 
minal arborisation  or  den- 
dron,  which  is  called  the 
nerve  endpJate.  Each  axon, 
on  entering,  gives  off  by 
division  several  branches 
like  antlers  :  in  amphibia 
these  branches  are  rodlike, 
long,  and  of  the  form  of 
baj^onets  ;  in  mammals  they 
are  crooked,  hook-like.  In 
all  instances,  however,  the 
divisions  are  unsymmetri- 
cal.  In  many  cases  the 
arborisation  of  the  endplate 
is  embedded  in  a  granular 
mass  of  protoplasm  con- 
taining oblong  nuclei.  This 
nucleated  protoplasm  is 
identical  with  the  substance 
of  the  sarcoglia,  or  the 
sarcoplasm  mentioned  on  a 
former  page.  When  the 
muscular  fibre  contracts, 
this  endplate  naturally  as-  Fig.  117.— Muscle  Spindle  of  the 
sumes  the  shape  of  a  pro-        ^'^l^^it  treated  with  gold  chio- 

t  J  i  iide.     (Kolliker,  II.) 

mmence  —  Boyere  s   nerve   „^  ^^^^,.^  q^,,,^  terminating'  iu  the 

Oiinoi'^if  ^^'npl^        mnQpnlnr  middle   p;iit  of  the   spiiidlt-  us  a 

lUOUlil.  JLaCil       mUbCUiai  spiral  endiDg  of  fine  Hbrils. 


i66 


Elements  of  Histology. 


libre  has  at  least  one  nerve  endplate,  but  occa- 
sionally has  several  in  near  pioximity.  Each  end- 
plate  is  generally  supplied  by  one  nerve  fibre,  some- 
times, however,  by  two.  The  contraction  wave 
generally    starts    from    the    endplate.       The    muscle 


Fiy;.  lis. — Termiuation  of  ilediillated  Nerve  Fibres  in  Tendon,  near  the 
Insertion  of  the  Striped  Muscular  Fibres.     (Golgi.) 

The  nerve  fibres  terminate  in  peculiar  arborising  eudplates  of  primitive 
fibrillae 


huds  of  KoUiker  or  muscle  spindles  of  Kiihne 
(mentioned  on  a  former  page)  contain  numerous 
medullated  nerve  fibres  with  lamellated  Henle's 
sheath,  and  these  nerve  fibres  terminate  in  the 
same  manner,  namely,  by  means  of  nerve  endplates 
(Fig.  117).  In  these  endplates  the  fine  nerve  fibres 
have  a  sj^iral  arrangement  (Ruffini).  These  are  con- 
sidered to  be  sensorv  end-organs.  According  to  Kol- 
liker,  from  the  primary  nerve  ending  of  the  mother 
fibre — i.e.  of  the  undiWded  portion  of  the  spindle — 
grow  out  the  ner\e  endings  for  the  thin  daughter 
fibres. 


PeRIPHERA  L    NeR  I  'E- EN  DINGS. 


167 


.-a 


Besides  this  iutra-musciilar  termination,  tliere 
is  a  plexus  of  tine  nev\e  fibres,  many  of  them 
said  to  terminate  with  free  ends,  situated  outside 
the  sarcolemma — i.e.  intermnscuh\r  ;  such  free  ends 
are  described  by  Beale,  Kolliker,  Krause,  and 
others.  Kolliker  and  Arndt  consider  these  intermus- 
cular     fibres 

as  sensory         ,.:^:v --  :^ 

nerves, 

161.  Ten- 
dons are  sup- 
plied w  i  t  h 
special  nerve 
endings, 
studied  by 
Sachs,  Rol- 
lett,  Gempt, 
Rauber,  and 
particularly 
G  olgi,  whose 
work  on  this 
subject  is  ex- 
tensive. These  terminations  are  most  numerous  near 
the  muscular  insertion.  They  are  of  the  follow- 
ing kinds  : — («)  A  medullated  nerve  fibre  branches 
repeatedly,  and  the  axis  cylinder,  after  having  lost 
the  medullary  sheath,  breaks  up  into  a  small  plate 
composed  of  a  dendritic  ramification  of  fine  primi- 
tive nerve  fibrils  (Fig.  118).  Owing  to  the  number  of 
the  fibrilla3  and  their  repeated  crossing,  it  is  difiicult  to 
say  whether  the  appearances  as  shown  in  Fig.  119  cor- 
respond to  a  real  network  or  to  a  dendron.  This  end- 
plate  is  occasionally  embedded  in  a  granular-looking 
material,  and  thereby  a  similar  organ  as  the  nerve  end- 
plate  in  muscular  fibres  is  produced  (Fig.  119).  (6)  In 
the  tendons  of  man  and  many  mammals  Golgi  has  shown 
that  nerve  fibres  terminate  in  peculiar  spindle-shaped 


Fig.  119. — One  of  the  Teriniual  Ramitk-atioiis  of  the 
previous  figure,  more  highly  magnified. 

rt,  Medullated  nerve  fibre ;  ft,  apiiareutly  reticulated 
endplate.    {Golgi.) 


i68 


Vj^I 


<. 


I 


Fig.  120. — Two  Tendon  Spindles  of  Golgi  in  tlie  rabliit,  sliowing  the  distri- 
bution and  spiral  terniination  ol'  the  nerve  fibres  ou  the  spindles.  {After 
K  oil  Her.) 


Per  I  pn  ERA  l  Ner  ve-en dings. 


169 


enlargements  of  tendon  Ijundles  (Fig,  120).  These 
tendon  spindles  of  Golgi  consist  each  of  two,  three,  or 
more  tendon  bundk's  within  a  common  sheath ;  a 
bundle    of   fine   medullated    nerve   fibres    enters    the 


Fig.  121.— Termination  of  Metlnllated  Nerve  Fibres  in  Tendon.     {Golgi.) 

a,  End-lnilbs  with  couvoliited  lueclullatecl  nerve  fibre ;  b,  end-bulb  similar  to  a 
Herlist's  corpuscle. 

spindle,  their  axis  cylinders  break  up  into  primitive 
fibril  he,  which  are  arranged  as  a  network  and  as 
spiral  fibrillar.  (c)  A  medullated  nerve  fibre  ter- 
minates in  an  end-lmlb  (Fig.  121),  similar  to  those  of 
the  conjunctiva,  or  of  a  Herbst's  corpuscle. 


170 


CHAPTER    XVI. 

THE    SPINAL    CORD. 

1  G2.  The  spinal  cord  is  enveloped  in  three  distinct 
membranes.  Tiie  outermost  one  is  the  dura  mater. 
This  is  composed  of  more  or  less  distinct  lamellag  of 
fibrous  connective  tissue  with  the  flattened  connective- 
tissue  cells  and  networks  of  elastic  fibres.  The  outer 
and  inner  surface  of  the  dura  mater  is  covered  with  a 
layer  of  endothelial  plates. 

163.  Next  to  the  dura  mater  is  the  extremely 
delicate  arachnoid  membrane.  This  also  consists  of 
bundles  of  fibrous  connective  tissue.  The  outer 
surface  is  smooth  and  covered  with  an  endothelial 
membrane  facing  the  space  existing  between  it  and 
the  inner  surface  of  the  dura  mater  ;  this  space  is  the 
subdural  lyniph  space.  The  inner  surface  of  the 
arachnoidea  is  a  fenestrated  membrane  of  trabeculse 
of  fibrous  connective  tissue,  covered  on  its  free 
surface — i.e.  the  one  facing  the  sub-arachnoidal  lympli 
space — with  an  endothelium. 

164.  The  innermost  memVjrane  is  the  pia  mater. 
Its  matrix  is  fibrous  connective  tissue,  and  it  is  lined 
on  its  outer  surface  with  an  endothelial  membrane. 
Also  the  inner  surface  facing  the  cord  j)roper  has  an 
endothelial  lining,  but  this  is  not  as  complete  and 
continuous  as  that  of  its  outer  surface.  Between 
the  arachnoid  and  pia  mater  extends,  from  the  fenes- 
trated portion  of  the  former,  a  spongy  f)lexus  of 
trabeculse  of  fibrous  tissue,  the  surfaces  of  the 
trabeculse  being  covered  Avith   endothelium.      By  this 


Sr/NA  L   Cord. 


lyr 


spongy  tissue — tho  snh-araclinoidal  tissue  (Key  and 
Ketzius) — the  subarachnoidal  space  is  subdivided  into 
a  labyrinth  of  areohe.  On  each  side  of  the  cord, 
between    the    anterior    and    posterior    nerve    roots, 


-•_»  j^f  J 

"  -^■'^v*! 


Fig.  12-2.— Transverse  section  tlirougli  the  Cervical  Cord  of  aeliild,  2  years 
old,  sliowing  well  the  anterior  wliite  commissure  and  the  numerous 
nieduUated  fibres  passing  horizontally  through  the  grey  matter  (col- 
laterals) from  and  to  the  white  columns.     {Weigcrt.) 

z,  Tract  of  Goll ;  B,  tract  of  Burdach ;  l,  tract  of  Lissauer. 


extends  a  spongy  fibrous  tissue,  called  ligamentuni 
denticidatiiin,  between  the  arachnoidea  and  pia.  By 
it  the  sub-arachnoid al  space  is  subdivided  into  an 
anterior  and  posterior  division. 

165.  The  subdural  and  sub-arachnoidal  spaces  do 
not  communicate  with  one  another  (Luschka,  Key 
and  Retzius). 


^7 


Elements  of  Histology. 


The  dura  mater,  as  well  as  the  arachnoid,  sends 
prolongations  on  to  the  nerve  roots  ;  and  the  sub- 
dural and  sub-arachnoidal  spaces  are  continued  into 
the  lymphatics  of  the  peripheral  nerves. 


li.C, 


Fig.  123a. — Transverse  section  of  the  Spinal  Cord  in  tlie  Cervical  region- 
{M icrophotog raph  of  Weigcrt-Pal  specimen.) 

p. E.  c,  Postero-extenial  column  ;C.g.,  postero-niedian  column  or  colmnu  of 
GoU  ;  p.  u.,  the  issuing  posterior  root ;  L.  c.  lateral  column  :  a.  f.,  anterior  or 
ventral  Assure.  The  white  matter  is  more  deeply  stained  than  the  more 
central  grey. 


All  three  membranes  contain  their  own  system  of 
blood-vessels  and  nerve  fibres. 

166.  The  cord  itself  (Fig.  122)  consists  of  an  outer 
or  cortical  part  composed  of  medullated  nerve  fibres  : 
the  ichite  matter,  and  an  inner  core  of  grey  matter. 
On    a    transverse     section    through    the     cord    the 


Spinal   Cord. 


17.3 


contrast  of  colour  between  the  white  mantle  and  the 
grey  core  is  very  conspicuous.  The  relation  between 
the  white  and  grey  matter  differs  in  different  parts  ; 
it  gradually  increases  in  favour  of  the  former  as  we 


P.E.C. 


L.H. 


L.C 


A.F. 


Fig.  123b. — Section  of  the  Spinal  Cord  in  the  Dorsal  region. 
{Micropliotograph  of  a  IVeigert-Pal  specimen.) 

Note  the  small  aiii<iunt  nf  grey  matter  wbich  project?  iHterally  at  level  L.  h.  to 
fonu  a  lateral  liorn.  Xote,  too.  at  tbe  same  level  on  the  median  side  of  tbe 
posterior  born  a  deflnite  mass,  forming  Clarke's  columns.  The  lettering  is 
as  in  the  section  through  cervical  region. 


ascend  from  the  lumbar  to  the  upper  cervical  portion 
(Figs.  123a,  123b,  123c).  The  grey  matter  presents 
in  every  transverse  section  through  the  cord  more  or 
less  the  shape  of  a  capital  H  ;  the  projections  being  the 
anterior  and  posterior  horns  or  cornua  of  grey  matter, 
and    the    cross-stroke    being    the    grey    commissure. 


174  Elements  of  Histology. 

In  the  centre  of  this  grey  commissure  is  a  cylindrical 
canal  lined  with  a  layer  of  columnar  epithelial  cells  ; 
this  is  the  central  canal ;  the  part  of  the  grey  commis- 
sure in  front  of  this  canal  is  the  anterior,  the  rest  the 
posterior,  grey  commissure.  The  shape  of  the  whole 
figure  of  the  grey  matter  differs  in  the  different 
regions,  and  this  difference  is  brought  about  by  the 
breadth  and  thickness  of  the  grey  commissure  as  also 
of  the  grey  horns  themselves.  In  a  section  through 
the  cervical  region  the  grey  commissure  is  long  and 
thin ;  in  the  dorsal  region  it  becomes  shorter  and 
thicker  ;  and  in  the  lumbar  region  it  is  comparatively 
very  short  and  thick.  Besides  this,  of  course,  the 
relative  proportions  of  grey  and  white  matter,  as 
mentioned  before,  indicate  the  region  from  which  the 
particular  part  of  the  cord  has  been  obtained.  In  the 
lower  cervical  and  lumbar  regions  where  the  nerves  of 
the  brachial  and  sacral  plexus  leave  or  join  the  cord 
respectively,  this  latter  possesses  a  swelling,  and  the 
gre}^  matter  is  there  increased  in  amount,  the  swelling 
being  in  fact  due  to  an  accumulation  of  grey  matter, 
with  which  additional  numbers  of  nerve  fibres  become 
connected  ;  but  the  general  shape  of  the  grey  matter 
is  retained. 

167.  The  cornua  of  the  grey  matter  are  generally 
thickest  in  the  line  of  the  grey  commissure  :  they 
become  thinned  out  into  anterior  and  posterior  edges 
respectively,  which  are  so  placed  that  they  point 
towards  the  antero-lateral  and  jDostero-lateral  fissures. 
The  anterior  horns  are  in  all  parts  thicker  and  project 
less  than  the  posterior,  and  therefore  the  latter  reach 
nearer  to  the  surface,  becoming  attenuated  and  passing 
into  the  posterior  nerve  roots. 

There  is  generally  a  third  projection  of  grey 
matter — the  lateral  horn  (see  Fig.  123  b).  This  is, 
however,  conspicuous  only  in  the  upper  two- thirds 
of  the  thoracic  cord. 


Spinal   Cord. 


175 


1G8.  The  white  matter  is  composed  chiefly  of 
medulhited  nerve  fibres  riuiiiin<,^  a  lon.<;itudinal  course, 
and  therefore,  in  a  transverse  section  through  the 
cord,  appear  in  cross-section.     They  are  arranged  into 


Fij 


123c.— Section  through  the  Spinal  Cord   in   the   Sacral  region. 
(Microphotogr((2^h  of  a  Weigert-Pal  speciinen.) 


Tlie  lighter  stained  trrey  matter  is  larpe  in  amount  compared  with  the  darker 
white  matter.  The  tips  of  tlie  posterior  horns  and  around  the  central  canal 
are  very  lightly  stained  owing  to  the  presence  of  much  substantia  tjclatinosa. 
Many  niedullated  fibres  are  seen  traversing  the  anterior  horns. 


cokimns,  one  anterior,  one  lateral,  and  one  posterior 
column  for  each  lateral  half  of  the  cord,  the  two 
halves  being  separated  by  the  anterior  and  posterior 
median  longitudinal  fissure.  The  anterior  median 
fissure    is    a    real    fissure  extending    in   a    horizontal 


176  Elements  of  Histology. 

direction  from  the  surface  of  the  cord  to  iiPAir  the 
anterior  grey  commissure.  It  contains  a  prolongation 
of  the  pia  mater  and  in  it  large  vascular  trunks.  The 
posterior  fissure  is  not  in  reality  a  space,  but  is  tilled 
up  by  neuroglia.  It  extends  as  a  continuous  mass  of 
neuroglia  in  a  horizontal  direction  from  the  posterior 
surface  of  the  cord  to  the  posterior  grey  commissure. 
The  exit  of  the  anterior  or  motor  nerve  roots  and 
the  entrance  of  the  posterior  or  sensitive  nerve  roots 
are  indicated  by  the  anterior  lateral  and  posterior 
lateral  fissures  respectively.  These  are  not  real  fissures 
in  the  same  sense  as  the  anterior  median  fissure,  but 
correspond  more  to  the  posterior  median  fissure, 
beinof  in  reality  filled  up  with  neuroglia  tissue,  into 
which  extends  a  continuation  from  the  pia  mater 
with  laro-e  vascular  trunks.  The  white  matter 
between  the  anterior  median  and  anterior  lateral 
fissure  is  the  anterior  column^  that  between  the 
anterior  lateral  and  posterior  lateral  fissure  is  the 
lateral  column,  and  that  between  the  posterior 
lateral  and  posterior  median  fissure  is  the  j^osterior 
column. 

169.  Besides  the  septa  situated  in  the  two  lateral 
fissures  respectively,  there  are  other  smaller  septa, 
neui^oglia  and  prolongations  of  the  pia  mater,  which 
pass  in  a  horizontal  and  radiating  direction  into  the 
white  matter  of  the  columns,  and  these  are  thus  sub- 
divided into  a  number  of  smaller  portions  ;  one  such 
big  septum  is  sometimes  found  corresponding  to  the 
middle  of  the  circumference  of  ont;  half  of  the  cord. 
This  is  the  median  lateral  fissure,  and  the  lateral 
column  is  subdivided  by  it  into  an  anterior  and 
posterior  division. 

Similarly,  the  anterior  and  posterior  columns  may 
be  subdivided  into  a  median  and  lateral  division 
(Figs.  123  a  and  125). 

170.  Some    of    these    various    subdivisions    bear 


Spinal  Cord. 


177 


definite     names     (Tiirk,      Charcot,     Goll,     Flechsig, 
Gowers)  : — 

{ct)  The  median  division  of  the  anterior  column  is 
called  the  direct  or  uncrossed  pyramidal  tract,  being 


Fig.    124. 


-Scheme  of  the  subdivision    of  the  White    Cohimns. 
Fleschsig  and  Kahler,  from  KolUker,  II.) 


{After 


P  V,  Direct  pyramidal  tract  of  anterior  white  column  ;  v  g,  ventral  ground  tract 
of  anterior  white  column  ;  a  L,antero-lateral  tract  of  lateral  column.  Gowers's 
tract;  s  r,  remainder  of  antero-lateral  part  of  lateral  column;  k  s,  direct 
cerebellar  tract  of  lateral  column  ;  p  s,  crossed  pyramidal  tract  of  lateral 
column.;  H  a,  tract  of  Burdach  of  posterior  white  column  ;  G,  tract  of  Goll  in 
posterior  column.  Grey  matter,  grey  commissure  around  central  canal, 
anterior  and  posterior  roots  left  unshaded. 


a  continuation  of  that  part  of  the  anterior  pyramidal 
tract  of  the  medulla  oblongata  [see  below)  that  does 
not  decussate  in  the  medulla. 

(h)  The  lateral  division  of  the  anterior  column  is 
the  ventral  or  anterior  ground  tract. 

(c)  The  direct  cerebellar  fasciculus  or  tract  is  the 
superficial  portion  of  the  postero-lateral  column  ;  it  is 

M 


lyS  Elements  of  Histology. 

a   direct    continuation    of  the    white    matter    of   the 
cerebellum. 

{d)  The  posterior  division  of  the   lateral  column 
inside  the  cerebellar  fasciculus  is  called   the  crossed 


Fig.  125 — Section  of  Spinal  Cord,  one  half  of  wliicli  (left)  shows  the  tracts 
of  the  white  matter  ;  and  the  other  half  (right)  shows  the  grouping  of 
the  ganglion  cells  in  the  grey  matter  (semidiagrammatic) .  {After 
Sherrington,  from  Kirke's  "  Physiology.") 

7, 10, 9,  and  3  are  tracts  of  descending  deseneration  ;  1,4, 6,  and  8  of  ascending 
degeneration  ;  1.  tract  of  CtoH;  2,  tract  of  Burdach;  3,  comma  tract;  4,  tract 
of  Lissauer  ;  all  these  belong  to  the  posterior  white  column  ;  6,  direct  cere- 
bellar tract ;  7,  crossed  pyramidal  tract  ;  8,  tract  of  Gowers  ;  9,  descending 
antero-lateral  trace ;  10,  direct  pyramidal  tract. 


pyramidal  fasciculus  or  tract,  being  a  continuation 
of  the  decussated  part  of  the  anterior  pyramidal  tract 
of  the  medulla  oblongata. 

(e)  The  lateral  division  of  the  posterior  column, 
with  the  exception  of  a  small  peripheral  zone,  is  the 
cuneiform  or  cuneate  Jasciculus,  or  the  tract  of 
Burdach, 


Spinal  Cord. 


179 


This  part  is  connected  directly  witli  the  median 
bundle  of  the  posterior  nerve  roots,  or  rather  by  the 
numerous  collaterals  passing  off  from  the  posterior 
root  fibres. 

(y')  Tiie  median  division  of  the  posterior  column 
is  called  the  J'ascicidus  or  tract  of  G oil. 

(g)  The  tract  or  fasciculus  of  Lissauer  (Fig.  125) 
is  a  small  mass  of 
white  fibres  situated 
between  the  outer  su- 
perficial portion  of  the 
tract  of  Burdach  and 
of  the  direct  cerebellar 
tract,  and  close  to  the 
posterior  lateral  fis- 
sure. 

In  addition  to 
these,  a  narrow  mass 
of  fibres  in  the  depth 
of  the  tract  of  Bur- 
dach, near  the  grey 
commissure,  represents 
a  separate  group,  called 

the  comma-shaped  tract :  and  the  superficial  mass  of 
white  matter  in  the  anterior  half  of  the  lateral  column, 
which  is  called  the  anterolateral  ascending  tract  of 
Gotcers  {see  Fig.  124). 

These  various  divisions  can  be  traced  from  the 
meduUata  oblongata  into  the  cervical,  and  more  or  less 
into  the  dorsal  part  of  the  cord  ;  but  farther  down 
many  of  them,  like  the  direct  cerebellar  tract  and  the 
tract  of  Goll,  are  lost  as  separate  tracts,  except  the 
crossed  pyramidal  fasciculus. 

Experiments  have  been  made  which  demonstrate 
that  these  different  tracts  are  physiologically  of  very 
different  character.  According  to  a  well-established 
law — the   AVallerian    law — each    nerve    fibre  has    its 


Fig.     12(3. — From    a    transverse    section 

"through  a    most    peripheral   part    of 

the  White  Matter  of  the  Cord.  {Atla^.) 

c.  Special  peripheral  collection  of  neu- 
roglia ;  w,  white  matter  with  the  medul- 
lated  nerve  fibres  shown  in  cross  section, 
and  nenroglia  between  them. 


So 


Elements  of  Histology. 


nutritive  centre  in  the  ganglion  cell  with  which  it  is 
connected,  and  if  a  nerve  fibre  is  cut,  that  part  which 
remains  connected  with  the  nutritive  centre  does  not 
degenerate,  while  that  part  severed  from  the  centre 
degenerates.     Consequently,  if  by  cutting  the  cord  at 


Fig.  127. — Stellate  Neuroglia  Cells  of  Golgi,  with  nimieroxis  ramifying  pro- 
cesses ;  from  the  cord  of  ox.     {EdlliJcer,  II.) 


a  particular  level  some  fibres  i-emain  intact  above  the 
section  but  degenerate  below,  they  show  descending 
degeneration  ;  they  have  their  nutritive  centre  above 
the  section  and  are  jDrobably  eflferent  fibres.  On  the 
other  hand,  those  fibres  w^hich  degenerate  above,  but 
remain  intact  below  the  section,  show  ascending 
degeneration  ;  they  have  their  nutritive  centre  below 
the  section  and  are  probably  aflerent  fibres. 

By    means     of   Weigert's    method    it   has    been 


Spinal   Cord.  i8r 

possible  to  show  (Weigert)  not  only  that  the  nerve 
fibres  constituting  tlie  white  cohimns  are  grouped  iu 
different  tracts  but  that  in  the  embryo  they  obtain 
their  medullary  sheath  at  different  but  definite  periods. 


.  / 


Fig.  12S. — Longitudinal  section  through  the  Lateral  White  Column  of  the 
Cord  of  the  Ox,  showing  the  axis  cylinders  of  the  meduUated  nerve 
fibres,  numerous  fine  longitudinal  and  transverse  fibrils  of  the  neu- 
roglia, and  tlie  stellate  neuroglia  cells  of  Golgi.  {After  Kolliker,  II. 
Highly  magnified.) 


Now  in  this  way  it  has  been  made  probable  that 
the  tracts  marked  in  the  figures  in  the  above-named 
divisions  of  the  anterior  and  lateral  columns  contain 
partly  efferent,  partly  afferent  fibres,  while  almost 
the  whole  of  the  fibres  of  the  posterior  columns  are 
afferent  ;  see  exolanation  of  figures, 


1 82  Elements  of  Histology. 

171.  Structure  of  the  cord. — The  most  im- 
portant and  fundamental  facts  which  have  been 
brought  to  light  within  recent  3"ears  concerning  the 
intimate  structure  of  the  white  and  grey  matter  and 
of  the  mutual  relations  of  the  different  parts  and  the 
different  elements  of  the  cord,  the  brain,  the  medulla, 
and  the  symj^athetic  system,  are  due  to  various  new 
methods  of  histological  examination,  as  also  to  the 
experimental  methods  of  section  of  the  cord  and  nerve 
roots  in  the  living,  and  observing  the  after-effects  as 
exhibited  by  degeneration  of  nerve  tracts.  As  regards 
the  histological  methods,  Weigert  and  Pal's  method  of 
staining  medullated  nerve  fibres  of  the  cord,  INIarchi's 
method  of  distinguishing  between  degenerated  and 
healthy  medullated  fibres,  and,  above  all,  Golgi's 
silver  method,  by  which  nerve  fibres  and  ganglion 
cells  can  be  easily  traced  in  their  finest  ramifications, 
have  been  the  means  of  o^Dening  uji  an  almost  new 
field  of  accurate  inquiry  concerning  all  parts  of  the 
central  nervous  system  as  well  as  of  the  special  senses. 
Golgi's  silver  method  has  enabled  himself,  and,  to  a 
very  conspicuous  degree,  Ramon  y  Cajal  and  Kolliker, 
to  bring  to  light  facts  concerning  the  intimate  struc- 
ture of  the  central  nervous  system,  the  ganglia,  and 
the  sense  organs,  which  stand  out  in  respect  of 
clearness  and  trustworthiness.  Other  histologists, 
Lenhossek,  Eetzius,  and  others,  have  by  this  method 
also  been  enabled  to  contribute  important  facts. 

172.  The  ^-oiiiid  substance  (Fig.  126)  of  both 
the  white  and  grey  matter — i.e.  the  stroma  in 
which  nerve  fibres,  nerve  cells,  and  blood-vessels  are 
embedded — is  a  peculiar  kind  of  connective  tissue, 
which  is  called  by  Yirchow  neuroglia  and  by 
Kolliker  supporting  tissue.  It  consists  of  three 
diffeient  kinds  of  elements  :  [a)  a  homogeneous  trans- 
parent semi-fluid  iiwtrio:,  which  in  hardened  sections 
appears  more  or  less  granular ;  {}>)  a  network  of  very 


Spinal  Cord. 


183 


delicate  fibrils — npurotjlia  fibrils — which  are  similar 
in  some  respects,  but  not  quite  identical  with  elastic 
fibres.       In    the    columns    of  the   wliite    matter   the 


p.m. 


Cty.o. 


a.c. 


Fig.  129.— Cross-section  of  the  central  part  of  the  Spinal  Cord  from  tlie 
Lumbar  region  of  an  Adult,  showing  the  central  canal,  its  lining  epithe- 
lium surrounded  by  neuroglia,  forming  the  central  grey  nucleus, 
(After  Schdfer.) 

/.a.,  Anterior  median  fissure;  p.m.c,  posterior  white  column  ;  ff.c,  anterior 
white  comniissure. 


fibrils  extend  chiefly  in  a  longitudinal  direction,  in 
the  gi'ey  matter  they  extend  uniformly  in  all 
directions,   and   in   the    septa    between    the    columns 


184 


Elements  of  Histology. 


they  extend  for  the  most  part  radially,  (c)  Richly 
branched  nucleated  cells  intimately  woven  into  the 
network  of  neuroglia  fibrils.  These  cells  are  the 
neuroglia  cells  or  glia  cells.  Golgi  was  the  first  to 
show  that  though  richly  branched  they  do  not  anasto- 
mose with  one  another.      The  sweater  the  amount  of 


^^%f|^NiS»/ 


1^ 


* 


Fig.  1:30a.— Cross-section  tlii-ongh 
central  canal  of  tlie  cord, 
sbowiug  the  lining  epithe- 
lium, from  a  child  of  sis. 
(After  Schdfer.) 


Fig.  130b.— CUiated  Epithe- 
lium lining  the  central 
canal  of  the  cord  in  a 
child  of  six,  more  highly 
magnified  than  in  Fig. 
130a.     {After  Scha/er.) 


neuroglia  in  a  particular  part  of  the  white  or  grey 
matter,  the  more  numerous  are  these  three  elements 
(Figs.  127  and  128). 

In  both  the  white  and  grey  matter  the  neuroglia 
has  a  very  unequal  distribution ;  but  there  are  certain 
definite  places  in  which  there  is  always  a  considerable 
amount — a  collection,  as  it  were,  of  neuroglia  tissue. 
These  places  are  :  («)  underneath  the  pia  mater — 
i.e.  on  the  outer  surface  of  the  white  matter  :  here 
most  of  the  neuroglia  fibrils  have  a  horizontal 
direction  ;  near  the  grey  matter  there  is  a  greater 
amount  of  neuroglia  between  the  nerve  fibres  of  the 
white  matter  than  in  the  middle  parts  of  this  latter  : 
in  the  septa   between   the  columns  and  between  the 


Spinal  Cord. 


18: 


divisions  of  columns  of  white  matter  ;  at  the  exit  of 
the  anterior  and  the  entrance  of  the  posterior  nerve 
roots. 

(6)  A  considerable    accumulation  of   neuroglia  is 
present  immediately  around  the  epithelium  lining  the 


Fig.  131.— Central  C'aual  of  the  Cord  of  a  Child,  1^  year  old  ;  the  cells  of 
ependyina  are  well  shown,  with  their  long  filamentous  processes. 
{Kdlliker,  II.) 


central  canal  ;  this  mass  is  cylindrical,  and  is  called 
the  central  grey  nucleus  of  KoUiker  (Fig.  129).  The 
epithelial  cells  lining  the  central  canal  are  conical, 
their  bases  facing  the  canal,  their  pointed  extremity 
being  drawn  out  into  a  fine  filament  intimately  inter- 
woven with  the  network  of  neuroglia  fibrils.  In  the 
embryo  and  young  state  (Figs.  130a  and  130b),  the 
free  base  of  the  epithelial  cells  has  a  bundle  of  cilia,  but 
in  the  adult  they  are  lost  amongst  the  epithelial  cells 


1 86 


Elements  of  Histology 


lining  the  central  canal  :  some  show  in  i:)reparations 
stained  after  Golgis  method  processes  of  extreme 
length  (Fig.  131). 

(<?)  Another  considerable  accumulation  of  neuroglia 
exists  near  the  dorsal  end  of  the  posterior  grey  horns, 
as  the  suh-^tnntia  gdotinos<i  of  Rolando. 

173.  The  white  uiatter  (Fig.  132)  is  composed, 
besides  neuroglia,  of  medullated  nerve  fibres  varving 
veiy  much  in  diameter,  and  forming  the  essential  and 

chief  part  of  it.   They 


possess  an  axis  cy- 
linder and  a  thick 
medullary  sheath 
more  or  less  lamin- 
ated, but  are  devoid 
of  a  neurilemma  and 
its  corpuscles.  Of 
course,  no  nodes  of 
Ranvier  are  observ- 
able. In  specimens 
of  white  matter  of 
the  posterior  co- 
lumns, Avhere  the 
nerve  fibres  have 
.  been  isolated  by  teas- 
ing after  hardening,  many  fine' medullated  libres  are 
met  with  which  show  the  varicose  appearance  mentioned 
in  a  former  chapter.  The  medullated  nerve  fibres, 
or  rather  the  matrix  of  their  medullary  sheath,  con- 
tains neurokeratin.  The  nerve  fibres  of  the  white 
matter  run  chiefly  in  a  longitudinal  direction,  and 
they  are  separated  from  one  another  by  the  neuroglia. 
Here  and  there  in  the  columns  of  white  matter  are 
seen  connective-tissue  septa  with  vessels,  by  which 
the  nerve  fibres  are  grouped  more  or  less  distinctly 
in  divisions. 

174.   Although    most    of    tiie    nerve   libres  con- 


Fig.  132. — From  a  transverse  section 
through  the  White  Matter  of  the  CorcL 

Showing  thetransversely-cat  medullated  nerve 
fibres,  the  neuroglia  between  them  with 
two  branched  neuroglia  cells.    (Atlas.) 


S/'/NAL  Cord.  187 

stituting  the  columns  of  white  matter  are  of  a 
longitudinal  direction — i.e.  passing  upwards  or  down- 
wards between  the  grey  matter  of  the  cord  on  the  one 
hand  and  the  brain  and  medulla  oblongata  on  the 
Other — there  are  nevertheless  a  good  many  medul- 
lated  nerve  fibres  and  groups  of  nerve  fibres  which 
have  an  oblique  or  even  horizontal  course. 

Thus  :  (1)  The  anterior  median  fissure  does  not  reach 
the  anterior  grey  commissure,  for  between  its  bottom 
and  the  latter  there  is  the  lohite  commissure  {see  Fig. 
129).  This  consists  of  bundles  of  medullated  nerve- 
fibres  passing  in  a  horizontal  or  slightly  oblique 
manner  chiefly  between  the  grey  matter  of  the  anterior 
horn  of  one  side  and  the  anterior  white  column,  in- 
cluding the  direct  pyramidal  tract,  of  the  opposite  side. 
This  anterior  white  commissure  is  in  respect  of 
position  a  continuation  of  the  decussation  of  the 
pyramidal  tract  in  the  lower  part  of  the  medulla 
oblongata.  As  mentioned  above,  this  latter  passes 
down  the  cord  as  the  crossed  pyramidal  tract  in  the 
inner  part  of  the  postero-lateral  column.  From  this 
it  follows  that  the  fibres  of  the  pyramidal  tract  of  the 
medulla  ultimately  all  cross  over  to  the  opposite  side 
of  the  cord.  The  majority  do  this  in  the  pyramidal 
decussation  of  the  medulla,  the  minority  descend  in 
the  cord  as  the  direct  pyramidal  tract,  but  its  fibres 
gradually  along  the  cord  cross  over  by  the  anterior 
white  commissure. 

(2)  The  medullated  nerve  fibres  constituting  the 
anterior  roots  of  the  spinal  nerves  leave  the  cord  at 
and  about  the  antero-lateral  fissure;  the  fibres  pass 
mostly  in  a  somewhat  oblique,  some  also  in  a  hori- 
zontal direction  through  the  white  matter  of  the  cord, 
and  each  of  them  originates,  some  sooner,  some  later, 
as  the  axon  or  axis  cylinder  process  of  a  ganglion 
cell  of  the  anterior  grey  horn.  This  is  the  fate  of 
most  of  the  anterior  root  fibres — that  is  to  say,  they  are 


1 88  Elements  of  Histology. 

primarily  tlie  axons  of  ganglion  cells  of  the  anterior 
grey  horn  of  the  same  side ;  this  axon  becomes 
invested  with  a  medullary  sheath,  and  as  an  efferent 
meduUated  nerve  fibre  passes  out  through  the  anterior 
nerve  roots.  It  is,  however,  probable  that  some  of 
these  fibres  are  axis-cylinder  processes  or  ax^ns  of 
ganglion  cells  of  the  anterior  horn  of  the  opposite 
side,  and  as  such  pass  through  the  anterior  commis- 
sure, while  a  small  number  of  anterior  root  fibres  can 
be  traced  into  the  posterior  grey  horn,  where  they  are 
evolved  as  the  axis  cvlinder  or  axon  of  a  sfanglion 
cell  of  this  part  of  the  grey  matter. 

As  will  be  mentioned  presently,  the  grey  matter 
of  the  cord  contains,  in  the  dorsal  or  thoracic  portion 
(between  the  seventh  cervical  and  second  or  third 
lumbar  nerve),  a  special  column  of  ganglion  cells — 
Clarke's  column  ;  the  axon  of  some  of  these  cells 
appears  to  pass  through  the  anterior  grey  horn  to 
join   the   anterior  root   fibres. 

But  according  to  Fleclisig,  with  whom  Kolliker 
agrees,  the  axons  of  most  of  the  ganglion  cells  of 
Clarke's  column  pass  in  a  horizontal  direction  from 
the  grey  matter  into  the  lateral  white  column,  where 
they  pursue  their  course  as  longitudinal  fibres  towards 
the  cerebellum,  thus  forming  the  fibres  of  the  direct 
cerebellar  tract. 

(3)  The  posterior  roots.  The  medullated  nerve 
fibres  constituting  the  posterior  roots  are  branches  of 
the  axis-cylinder  process  of  the  ganglionic  cells  of  the 
spinal  ganglion  ;  they  enter  the  cord  as  small  bundles 
by  the  postero-lateral  fissure,  betw^een  the  lateral  and 
posterior  columns  of  white  matter,  in  a  slightly 
slanting  direction,  and  at  the  same  time  turned  more 
towards  the  posterior  column  of  white  matter.  Now 
the  fibres  of  the  posterior  roots  may  be  roughly 
grouped  into  a  lateral  and  mediau  bunale,  the  former 
containing  predominantly  fine  medullated  fibres,  the 


Spinal  Cord.  189 

latter  predominantly  larger  niedullated  fibres  ;  the 
former  as  well  as  th(^  latter,  after  their  entry  into  the 
cord,  sooner  or  later  divide,  each  into  an  ascendiny 
and  a  descending  medullated  fibre.  The  ascending 
and  descending  fibres  resulting  from  the  division  of 
the  fibres  of.  the  Literal  bundle  form  part  of  and 
pursue  their  longitudinal  course  in  that  portion  of  the 
posterior  white  column  which  lies  next  to  the  posterior 
grey  horn  and  the  lateral  white  column,  and  which 
is  known  as  Lissauer's  tract  or  Lissauer's  bundle  {see 
Fig.  122).  The  ascending  and  descending  medullated 
fibres  resulting  from  the  division  of  the  fibres  of  the 
median  bundle  also  following  a  longitudinal  course 
are  distributed  principally  over,  and  form  part  of,  the 
white  matter  of  the  posterior  columns  (Burdach's  and 
GoU's  tract).  Some  of  these  fibres  are  said,  however, 
to  enter  directly  into  the  grey  matter  of  the  posterior 
horn  and  to  terminate  there. 

(4)  All  medullated  fibres  constituting  the  dififerent 
columns  of  white  matter  and  descendinof  or  ascending 
respectively  in  the  cord  send  out  at  numerous  levels 
horizontal  fibres  which  enter  or  pass  out  from  the 
grey  matter.  The  discovery  of  these  fibres  by  Golgi 
and  II anion  y  Cajal  by  means  of  the  silver  method 
constitutes  a  fundamental  advance  in  our  knowledoe 
of  the  minute  anatomy  and  physiology  of  the  cord. 
These  horizontal  fibres  which  branch  ofi' from,  or  join 
respectively,  the  fibres  constituting  the  different  tracts 
of  the  white  matter  are  called  collaterals  {see  Figs. 
122  and  123  c).  The  collaterals  give  off  branches 
themselves.  By  means  of  the  collaterals  and  their 
branches  numerous  connections  are  formed  between 
the  longitudinal  fibres  of  the  white  columns  on  the 
one  hand  and  the  grey  matter  on  the  other.  The 
collaterals  terminate,  or  originate  respectively,  near 
and  around  nerve  cells  in  all  jjarts  of  the  grey  matter 
hy  means  of  arborisations  or  dendrons  (Fig.  133). 


igo 


Elements  of  Histology. 


175.  As  mentioned  just  now,  collaterals  are  not 
limited  to  any  one  tract  of  the  white  columns,  and  are 
not  limited  to  any  particular  level,  but  are  given  off 

or    pass    into    re- 
spectively    the 
longitudinal  fibres 
constituting      the 
white  columns  in 
general      and     at 
level 
which 
of     the 
made. 


e  ^'  e  r  y 

through 

sections 

cord     are 

Figs.  122  and  123c 


give    a 


good 
presentation 
these  facts. 


re- 

of 


F  o  1  lowi  ng, 
then,  the  longi- 
tudinal medul- 
lated  fibres  con- 
stituting those 
tracts  of  white 
matter,  which 

were  described 
above  as  descend- 
ing fibres  (show- 
ing descending  de- 
generation) —  e.g. 
the  direct  pyra- 
midal tract,  the 
crossed  pyramidal 
tract,  the  inner 
portion  of  the  an- 
terior part  of  the  lateral  column — -it  is  seen  that 
at  many  points  each  sends  out  horizontal  colla- 
terals  which   enter   the  grey   matter   and    terminate 


Fig.  133. — Collaterals  passing  from  fibres  of 
posterior  column  into  the  grey  matter,  and 
teiTuinatiug  at «  by  dendrons.  From  the  cord 
of  a  newlj'-born  child.     {After  Kolliker,  II.) 


Spina  l   Cor d.  191 

there  as  arborisations  or  dendrons  close  to,  or  around, 
ganglion  cells  ;  and  similarly  the  longitudinal  medul- 
la ted  fibres  constituting  those  tracts  of  white  matter 
spoken  of  above  as  ascending  tracts — e.g.  the  tract  of 
Goll,  of  Burdach,  of  Lissauer,  the  dii-ect  cerebellar 
tract  and  the  superficial  parts  of  the  anterior  portion 
of  the  lateral  column  (Gowers's  tract) — are  connected, 
brought  into  relation,  by  means  of  collaterals  and 
their  dendrons,  with  the  grey  matter  and  with  the 
ganglion  cells  situated  in  the  latter.  The  bundles  of 
fine  nerve  fibres,  so  conspicuous  in  every  horizontal 
section,  passing  in  a  horizontal  manner  from  the 
posterior  columns  through  and  around  the  suhstantia 
gelatinosa  of  Rolando  of  the  posterior  grey  horn,  are 
bundles  of  collaterals  given  off  by  the  longitudinal 
fibres  of  the  posterior  columns. 

176.  The  grey  matter  of  the  cord  contains  the 
same  kind  of  neuroglia  as  the  white  matter — viz.  neu- 
roglia  fibres  and  neuroglia  cells  ;  the  fibres  do  not, 
however,  form  longitudinal  networks  as  in  the  white 
matter — due  to  the  peculiar  (longitudinal)  arrange- 
ment of  the  nerve  fibres — but  are  distributed  more  or 
less  as  a  uniform  network  ;  every  section,  therefore, 
be  it  longitudinal  or  transverse,  shows  the  glia  fibrils 
cut  transversely,  obliquely  and  longitudinally.  The 
glia  cells  are  the  same  in  size  and  in  their  numerous 
branched  processes  as  in  the  white  matter. 

In  this  matrix  of  neuroglia  are  embedded  nerve 
cells  or  o-anolion  cells  and  nerve  fibres  and  their 
ramifications.  The  ganglion  cells  are  all  possessed  of 
several  processes,  and  are  therefore  multipolar  ;  they 
differ  in  respect  (ci)  of  position,  {b)  of  size,  (c)  of 
the  structure,  distribution  and  connections  of  their 
processes. 

177.  (a)  ill  respect  of  position,  the  nerve  cells 
form  groups  and  aggregations  which,  in  the  longitu- 
dinal   axis   of    the    grey    matter^   are    more    or    less 


192  Elements  of  Histology. 

discontinuous,  so  tliat  to  each  particular  spinal  nerve 
or  segment  corresponds  a  more  or  less  separate  mass. 
The  following  groups  can  be  distinguished  on  each 
side  (Fig.  125)  : — 

(1)  The  centro-lateral  group,  situated  in  that  part 
of  the  anterior  cornu  which  is  in  contact  with  the 
ventral  portion  of  the  lateral  column ; 

(2)  The  dorso-Jateral  grotip,  also  situated  laterally 
in  the  anterior  cornu  immediately  behind  or  dorsal ly 
to  the  tirst-named  group  ; 

(3)  The  ventro-median  group,  situated  in  the 
foremost  portion  of  the  anterior  cornu  where  this  is 
in  contact  with  the  anterior  column  ; 

(4)  The  dorso-Tiiedian  group,  immediately  behind 
the  former — i.e.  next  the  anterior  white  commissure. 

(5)  As  mentioned  above,  that  portion  of  the  grey 
matter  which  projects  laterally  between  the  anterior 
and  posterior  cornu  of  each  side  and  about  midway 
(Figs.  122  and  125) — i.e.  the  lateral  cornu — -contains 
in  the  upper  two-thirds  of  the  thoracic  cord  groups  of 
ganglion  cells  which  represent  the  cells  of  the  lateral 
horn,  but  they  are  present  only  as  scattered  ganglion 
cells  in  the  corresponding  portion  of  the  grey  matter 
above  and  below  the  proper  lateral  horn  (Waldeyer). 

(6)  Throughout  the  thoracic  cord  there  is  present 
a  conspicuous  group  of  ganglion  cells,  which  groujD  is 
in  cross-section  of  a  rounded  or  oval  shape  ;  this  is  the 
2)osterior  vesicular  column  of  Clarke  or  Stilling's  group^ 
and  is  situated  at  about  the  same  level  as  the  group 
of  cells  in  the  lateral  horn  ;  but  while  this  latter  is 
lateral,  the  column  of  Clarke  is  situated  medially, 
and  it  has  to  be  added  that  it  really  belongs  more 
to  the  base  of  the  posterior  cornu.  These  two  groups 
5  and  6  belong  therefore  to  the  middle  region  of  the 
grey  matter. 

(7)  The  posterior  cornu  contains  in  all  parts 
only  scattered  cells   not  definitely  grouped.  Like  those 


Spinal   Cord.  193 

mentioned  in  the  anterior  cornu  and  the  middle 
region  of  the  grey  matter.  Also  in  the  substantia 
gelatinosa  of  Rolando  occur  solitary  ganglion  cells. 
Amongst  the  cells  of  the  posterior  cornu  the  so- 
called  marginal  cells  of  Waldeyer  and  Lissauer 
deserve  special  mention ;  they  are  situated  at  the 
margin  of  the  posterior  horn,  or  rather  of  the  sub- 
stantia gelatinosa,  where  this  is  in  contact  with  the 
dorsal  and  lateral  columns  of  white  matter.  The 
marginal  cells  are  long  and  spindle-shaped  and 
different  from  most  other  cells  of  the  posterior  cornu 
in  their  being  possessed  of  a  distinct  axon  or  axis- 
cylinder  process. 

178.  {h)  In  respect  of  size  the  ganglion  cells 
show  considerable  differences ;  the  biggest  cells  are 
those  of  the  anterior  cornu  mentioned  as  groups  1, 
2,  and  3  ;  the  cells  of  these  groups  measure  about 
70 — 130yu  in  diameter  ;  while  those  of  group  4,  dorso- 
median  group  of  the  anterior  horn,  are  considerably 
smaller,  30 — 80  ^ ;  between  these  two  sizes  are  the 
cells  of  the  lateral  horn  and  of  Clarke's  column, 
while  those  of  the  posterior  cornu,  with  few 
exceptions,   are   comparatively   small  cells. 

179.  (c)  111  respect  of  structHre  each  gan- 
glion cell  possesses  a  vesicular  nucleus  with  a  promi- 
nent nucleolus,  and  the  substance  of  the  cell  is  in  all 
cases,  when  examined  in  the  fresh  state  or  in  suitably 
prepared  specimens,  of  the  nature  of  a  more  or  less 
fibrillated  substance,  between  which  a  finely  granular 
matrix  can  be  recognised  (M.  Schultze).  The  fibrillse 
are  grouped  in  bundles,  and  appear  continuous  and 
radiating  from  around  the  nucleus  towards  and  into 
the  fibrillated  processes  ;  around  the  nucleus  the 
fibrillEB  appear  more  or  less  concentrically  arranged. 
In  the  anterior  cornu  the  ganglion  cells  contain 
normally  pigment  granules  grouped  near  and  around 
the  nucleus  (Klonne  and  Midler)  {see  Fig.  134). 


194 


Elements  of  Histology. 


Between  the  fibrill?e  constituting  the  substance 
of  the  ganghon  cells  are  found  masses  of  granules 
(distinct  from  the  just-mentioned  pigment)  which 
take  the  stains  well  :  these  are  the  chromatic  granules 
of  Nissl.     In   some   ganglion   cells  they  are  distinct 


Fig  134. — Section  tlirougli  the  Lower  Lumbar  Cord  of  Man.     After  a  pre- 
paration of  Klonne  and  Mailer  in  Berlin.     {Kdlliker,  11.) 

^y,  White  lateral  column  in  cross-section  ;  g,  grey  matter  of  anterior  liorn, 
showing  ganglion  cells  with  pigment  granules,  and  many  meduUated  nerve 
fibres. 


and  conspicuous,  in  others  less  so.  The  presence  of 
these  chromatic  granules  indicates,  it  is  suggested,  a 
phase  or  phases  of  normal  activity  of  the  ganglion 
cells,  whereas  their  disappearance  and  absence  cor- 
responds to  a  pathological  state  of  diminished  or 
abnormal  function. 

180.  The    most    important   differences,^  however. 


Spinal  Cord. 


195 


are    noticed  on  the  ganglion    cells  with    regard  to  the 
nature  and  coniKM^tioniS   of  their   processes. 

As  mentioned    on    a  previous    page,  all    ganglion 
cells  of  the  cord  are  multipolar  ;  amongst  the  processes 


Fig.   133. — Isolated  Ganglion  Cell  of  the  Anterior  Horn   of  the   Human 
Cord.     (Gerlach,  in  Strieker's  "  Manual  of  Histology.") 

o,  Axis  cylinder  process;  6,  pitrinenr..  The  braucUed  dendrites  of  the  ganalion 
cell  break  up  into  the  fine  arborisation  shown  in  the  upper  part  of  the 
figure. 


into  which  the  substance  of  the  cells  is  continued 
there  is  one,  occasionally  two,  which  become  sooner 
or  later  the  axis  cylinder  of  a  medullated  nerve 
fibre  ;  this  is  the  axon  or  neuraxon  of  the  ganglion 


196 


Elements  of  Histology. 


cell   (Fig.    135).      Such  an  axon  is  seen   to  come  otf 
from  each  of  the  ganglion  cells  of  the  anterior  cornu 


Fig.    136.  —Isolated    Multipolar    Gauglioii   Cell  ;of  the    Grey  Matter  of 
the  Cord.    {Gerlacli,  in  Strieker's  Manual.) 

The  dendritically-branclied  processes  (dendrites)  break  up  into  the  flue 
arborisation  into  which  is  seen  to  pass  a  fine  nerve  fibre  and  its  ramiflca- 
tion  derived  from  a  posterior  nerve  rf)Ot  fliire. 

and  of    Clarke's  column,    and  of   some   cells    in    the 
posterior   cornu.      The  axon  of  most  of  the  anterior 


Spina l  Cord.  1 9 7 

cells  is  continued  as  the  axis-cylinder  process  of  a 
medullated  nerve  fibre  passing  out  as  an  anterior 
root  fibre.  The  axon  of  other  cells  in  the  anterior 
cornu,  as  also  to  a  lesser  extent  of  the  posterior 
cornu  (including  those  of  the  substantia  gelatinosa), 
does  not,  however,  pass  into  anterior  root  fibres,  but 
becomes  the  axon  of  longitudinal  medullated  nerve 
fibres  forming  part  of  the  lateral,  and  to  a  lesser 
extent  the  anterior,  columns  of  white  matter. 

These  important  facts  were  discovered  by  Golgi 
and  Ramon  y  Cajal,  and  were  confirmed  by  KoUiker. 
According  to  Golgi  and  Ramon  y  Cajal,  axis-cylinder 
processes  or  axons  of  ganglion  cells  from  all  parts  of 
the  grey  matter  may  pass  into  the  anterior  commissure. 

Cells  of  this  character — i.e.  possessing  axons 
which  pass  as  longitudinal  medullated  fibres  into  the 
white  columns — are  Kolliker's  "  Tract  cellsJ^ 

181.  Another  very  striking  fact  discovered  by  Golgi 
and  by  Ramon  y  Cajal  is  this  :  that  the  axon  of  the 
ganglion  cells  ramifies.  In  some,  like  those  cells  of 
the  anterior  cornu,  whose  axon  passes  into  an  anterior 
root  fibre,  the  axon  for  some  distance  gives  off  few 
or  no  branches  (Golgi's  group  A).  In  other  cells,  like 
those  of  the  posterior  cornu,  the  axon  is  much 
branched  and  its  fibres  are  lost  in  the  grey  matter 
(Group  b).  The  former  are  considered  by  Golgi  as 
motor,  the  latter  as  sensory  cells. 

Besides  the  axon,  all  ganglion  cells  in  all  parts  of 
the  grey  matter  possess  more  or  less  numerous  pro- 
cesses which,  owing  to  their  rich  and  dendritic 
branching  and  their  distinctly  fibrillated  nature,  are 
the  protoplasmic  or  branched  processes,  or  the  den- 
drites (Fig.  136).  In  the  cells  of  the  anterior  cornu,  in 
those  of  Clarke's  column  and  of  the  lateral  horn,  the 
dendrites  are  numerous  and  distinctly  arborescent ; 
they  are  less  numerous  in  the  cells  of  the  posterior  cornu ; 
thicker  branches  give   off  laterally  smaller  branches, 


198 


Elements  of  Histology 


which  by  euntinut'il  raniiticatioii  become  greatly  attenu- 
ated and  ultimately  resolve  themselves  into  arbores- 
cent terminations  or  dendrons  (Fig.  136). 

While  the  dendrites  and  their  terminal  dendrons 
of  most  of  the  ganglion  cells  are  distributed  in  the 
grey  matter,  Golgi  has  proved  that  of  some  cells 
some  of  the  dendrites  pass  into  and  are  distributed 
amongst   the    nerve  fibres    of    the  white    columns,   a 


S' 


'F 


Fig.  137. — From  the  Lateral  Horn  of  the  Cervie<il  CoM  of  the  Ox.     Highly 
magnified.     (KoUiker,  II.) 

s,  Lateral  colanin  of  white  matter  in  cross-section ;  F,  fine  dendrites  of  the 
ganglion  cells  penetrating  into  the  white  cc^ituran. 


fact  wliieh  Kolliker  has  emphasised,  and  whicli  par- 
ticularly holds  good  for  the  cells  of  the  lateral  horn 
in  the  cervical  cord  of  the  ox.     (Fig.  137.) 

182.  Besides  the  ganglion  cells,  their  axons,  den- 
drites and  dendrons,  the  grey  matter  contains  nerve 
fibres  of  a  ditierent  origin  and  connection.  As 
mentioned  on  a  former  page  collaterals  of  longitu- 
dinal fibres  of  all  white  tracts  enter,  or  pass  out 
respectively  from  the  grey  matter  :  here  they  ramify 
and    terminate  1)V   arborisations  or  dendrons,    wliicli 


Spinal  Cord. 


199 


are  either  interiningliiig  with,  or  surrounding  the 
arl>orising  dendrons  of  the  dendrites  of  ganglion  cells 
or  surround  the  hody  of  the  ganglion  cells.  Owing  to 
the  great  number  of  such  collaterals,  as  mentioned 
on  a  former  page, 
their  arborisations 
or  dendrons  form  a 
considerable  por- 
tion of  the  grey 
matter. 


Sherrington  sug- 


gests 


W.W 


the  term  of 
synapsis  {avv  and 
(tTr-w)  as  indicating 
the  contiguous  but 
not  continuous  re- 
lation of  the  arbo- 
rising terminations 
of  axons  surround- 
ing the  arborising 
dendrites  or  the 
body  of  a  ganglion  ■m\^ 
cell.  Such  synapsis 
would  then  occur 
everywhere  in  the 
central  nervous  sys- 
tem    (cord,     brain, 

medulla,  Sympa-  t^ig-  137A.-Scheme  of  the  Elements  of  the  Conl 

,       .        '  T  concerned  in  Reflex  Actions.    Longitudinal 

thetlC     ganglia,     re-      view.     (Kdlliker,II.) 

where  .s-  rj,  Ganglion  cell  of  a  spinal  ganglion  ;  s,  sen- 
sory flhre  coming  from  the  periphery;  sth, 
division  of  a  posterior  root  fibre  into  sa,  an 
ascending  and  descending  fibre;  sc,  collaterals 
of  same  passing  to  motor  ganglion  cells,  m  ; 
m  ('•,  motor  (anterior)  root  fibres  being  axons  of 
anterior  nerve  cells. 


tina,      etc. ) 
neuraxons  and  their 
collaterals  of  a  near 
or  distant  ganglion 


cell    arborise    ( ter- 

minate)    around    dendrites    or    the    cell    body    of    a 

ganglion  cell. 

A  second,   also  considerable,  portion   of  the  grey 


200 


Elements  of  Histology. 


— L/i<? 


ns 


matter  is  made  up  of  dendrons,  the  developing  fibres 
of  which  are  not  collaterals  but  are  direct  con- 
tinuations of  longitudinal  fibres  of  the  white  columns; 
thus  the  descending  branches  of  posterior  root  fibres 
terminate  in  this  way   in  the  grey  matter,  many  of 

the  main  fibres  of  the 
anterior  and  particularly 
the  lateral  columns  pass 
into  or  pass  from  the  grey 
matter,  and  after  a  shorter 
or  longer  course,  either  on 
the  same  side  or  after 
crossing  through  the  an- 
terior or  posterior  com- 
missure terminate  as  den- 
drons around  ganglion 
cells  or  intermingle  with 
the  arborisations  of  den- 
m  IV  drites  of  ganglion  cells. 
The  manner  of  the  most 
probable  connections  and 
actions  of  the  grey  matter 
of  the  cord  are  illus- 
trated by  the  accom- 
panying diagrams  (Figs. 
137a  and  137b),  copied 
from  Kolliker. 

Before  the  introduc- 
tion of  the  method  of 
Weigert,  and  its  modifi- 
cation by  Pal  (by  which 
the  medullary  sheath  of 
nerve  fibres  is  stained), 
it  was  unknown  that  the  o'rev  matter  of  the  cord 
contains  medullated  nerve  fibres  to  any  large  extent. 
By  the  above  methods,  if  successfully  applied  to  the 
examination  of  suitablv  stained  sections  of  the  cord. 


miv 


Fig.  137e.— Scheme  of  the  Con- 
duction of  Inipiilses  in  Volun- 
tary Movement.    (Kolliker,  II.) 

2>s,  Fibres  of  the  crossed  pyramidal 
tract  in  the  cord ;  these  fibres  had 
crossed  (pyramidal  crossing)  m 
the  medulla  ;  collaterals  of  these 
fibres  pass  into  and  terminate 
in  the  grey  matter  of  the  cord  : 
p  o,  fibres  of  the  direct  pyramidal 
tract  in  the  cord,  collaterals  cross 
in  the  cord ;  m,  nerve  cells  in  the 
anterior  grey  horns;  7?i.  if,  axons 
of  same  forming  the  fibres  of  the 
motor  (anterior)  roots. 


Spinal   Cord.  201 

it  is  shown  that  tlie  grey  matter  contains  a  really 
astonishing  number  of  medullated  nerve  fibres,  run- 
ning singly  or  in  small  bundles,  horizontally  and 
obliquely.  All  the  above  collaterals,  as  also  the 
continuations  of  the  fibres  passing  from  the  white 
columns  into  the  grey  matter,  or  vice  versd,  are 
medullated  fibres  {see  Figs.  122  and  123a). 

183.  The  large  vascular  branches  enter  the  white 
matter  of  the  cord  from,  or  pass  out  by  way  of  the  pia 
mater,  being  invested  in  neuroglia  continuous  with 
the  tissue  of  the  pia  mater.  By  continued  division 
they  resolve  themselves  into  fine  branches,  which  pass 
into,  or  pass  from,  the  network  of  capillaries. 

The  capillaries  are  more  abundant  and  form  a 
more  uniform  network  in  the  grey  than  in  the 
white  matter.  In  the  latter  most  of  them  have  a 
course  parallel  to  the  nerve  fibres,  i.e.  longitudinally. 
The  blood-vessels  and  the  orano^lion  cells  are  ensheathed 
in  lymph  spaces  (perivascular  and  pericellular  spaces). 


202 


CHAPTER     XVII. 

THE    MEDULLA    OBLONGATA    OR    SPIXAL    BULB. 

184.  As  the  cervical  portion  of  the  spinal  cord 
passes  into  the  medulla  oblongata  its  parts  alter  in 
position  and  relation.  It  is  possible,  to  a  large 
extent,  to  recognise  in  the  bulb,  regions  which 
correspond  to  different  areas  of  the  cord.  Many  of 
the  cord  areas  are,  however,  lost  in  the  bulb,  and  on 
the  other  hand,  many  new  areas  appear. 

185.  The  anterior  or  ventral  fissure  is  continued 
as  far  as  the  bulb  extends.  The  posterior  or  dorsal 
fissure  of  the  cord  is  also  continued  for  a  certain 
distance  along  the  medulla,  but  this  widens  out  in  the 
upper  part  of  the  bulb  into  the  lower  end  of  i\\e  foui^th 
ventricle.  The  line  of  origin  of  the  anterior  roots  of 
the  spinal  cord  is  continued  into  the  medulla,  being 
marked  out  by  the  exit  of  the  roots  of  the  hypoglossal 
nerve.  In  the  upper  portion  of  the  medulla  this  line 
of  origin  develops  into  a  marked  fissure.  The  shallow 
groove  existing  dorsally  between  the  postero-median 
and  postero-external  columns  of  the  cord  is  even  better 
marked  in  the  bulb,  and  divides  the  funiculus  gracilis 
(median)  from  the  funiculus  cuneatus  (external). 
The  postero-lateral  groove  into  wliicli  the  posterior 
roots  pass  to  the  cord  is  continued  up  as  the  external 
boundary  of  the  funiculus  cuneatu.s  and  the  internal 
boundary  of  yet  another  longitudinal  projection, 
leading  u]3  to  a  prominence,  the  tubercle  of  Rolando. 
In  the  upper  portion  of  the  cervical  cord  there  project 
from    the    lateral    columns    the    roots    of   the    spinal 


Med ul la    Oblo nga  ta . 


203 


accessory  nerve.  The  line  of  origin  of  these  roots  is 
continued  up  along  the  lateral  surface  of  the  bulb  and 
there  arise  successively  along  this  line  the  roots    of 


Fig.  138.— Section  through  the  Lower  Eud  of  the  Pyramidal  Decussation. 
The  section  is  slightly  distorted.  {Microphotograph  of  section  stained 
with  aniline  Nue-blacl-.) 

A.  F.,  Anterior  or  ventral  Assure  lying  obliquely  on  accountiof  fibres  passing  from 
crossed  pyramidal  tract  on  left  side  to  anterior  column  on  risht ;  p.  k.,  pos- 
terior Assure  ;  i.  f., corresponds  to  septum  l)etweenGoirs  columnand  postero- 
external column  :  p.  li.,  posterior  root  of  first  cervical  nerve ;  on  the  left  side 
at  level  a.  h.  the  anterior  horn  is  separated  from  rest  of  grey  matter.  The 
substantia  gelatinosa  at  tip  of  posterior  horn  is  increased,  and  the  angle 
between  the  posterior  horns  is  greater  than  below. 


the  spinal  accessory,  the  vagus,  and  the  glosso- 
jyharyngpxd.  At  the  junction  of  the  bulb  with  the 
pons  the  seventh  nerve  passes  out  in  the  same  line,  and 
passing  through  the  substances  of  the  pons  \\\q  fifth 
nerve  possesses  a  corresponding  origin. 


204 


Elements  of  Histology. 


186.  It  will  be  found  most  convenient  in  order 
to  determine  the  relation  of  the  different  regions  in 
the  bulb  with  those  of  the  cord,  to  examine  the 
appearances  presented  by   successive  sections  of  the 


Fig.  139.— Section  thi'ougli  the  Upper  Part  of  the  Pyramidal  Decussation 
in  the  Medulla  Oblongata.     {Microphotograph  of  a  Weigert-Pal  specimen.) 

A.F.,  Remains  of  anterior  Assure;  the  dark  mass  immediately  above  consists 
of  the  decussating  pyramidal  fibres  ;  at  the  level  A.  H.  is  a  light  mass  on 
either  side  represeatinff  the  remains  of  anterior  liorn;  at  tue  level  c.  c.  in 
the  middle  line  is  the  grey  matter  round  the  central  canal ;  the  posterior 
nuclei  are  not  clearly  distinguishable. 


bulb,  cut  in  a  dorso-ventral  direction,  and  com- 
mencing at  a  level  immediately  above  the  cervical 
spinal  cord. 

187.   The  region  of  the  pyraiiiiclal  decus- 
sation (Figs.  138  and  139). — In  this  region  the  fibres 


Mrd  ul  l  a    Ob  long  a  ta  . 


205 


of  the  crossed  pyramidal  tract,  lying  in  the  dorsolateral 
portion  of  the  cord,  take  on  an  oblique  course  and, 
passing  across  the  middle  line,  again  resume  their  direct 
course  in  what  would  correspond  in  the  cord  to  the 


P.F. 


•c.c 


S  D. 


M. 


A.F. 


Fig.  140.— Section  through   the   Medulla  Oblongata   at   the  level  of  the 
Sensory  Decussation.     {Photograph  of  a  Weigert-Pal  specimen.) 

The  section  has  not  involved  the  olives  ;  the  pyramids  are  completely  formed 
and  project  at  p,  and  extend  inwards  as  far  as  the  level  sr,  meeting  in  the 
middle  line.  At  level  of  c.c.  on  middle  line  is  the  central  canal,  and  at  a 
short  distance  from  this  are  seen  numerous  fibres  arching  round  and  decus- 
sating on  middle  line  at  level  s.u. ;  k,  lies  between  funiculi  gracilis  and 
cuneatus. 


anterior  or  ventral  column.  In  their  passage  across  to 
the  other  side  of  the  medulla  these  fibres  separate  oft' 
the  head  of  the  anterior  horn  so  that  the  grey  matter 
of  the  cajnit  lies  in  the  anterior  area  disconnected 
from  the  main  mass  of  the  grey  matter.  The  angle 
formed  by  the  median  boundaries  of  the  two  posterioi^ 


2o6  Elements  of  Histology. 

horns  increases  very  considerably,  so  that  these  horns 
come  to  lie  more  transversely  across  each  half  of  the 
medulla  than  was  the  case  in  the  cord.  There 
develop  also  from  this  inner  margin  of  the  posterior 
horns,  in  the  iij)per  part  of  the  pyramidal  decussation, 
certain  protuberances  of  grey  matter  ;  a  median  mass 
projecting  into  the  funiculus  gracilis  and  known  as  the 
mideus  of  the  funiculus  gracilis  Rud  a  more  externally 
situated  mass,  projecting  into  the  funiculus  cuneatus, 
and  known  as  the  nucleus  of  the  funiculus  cuneatus. 
The  substantia  gelatinosa  at  the  tip  of  the  posterior 
horn  also  becomes  more  conspicuous  and  causes  the 
medulla  to  project  in  this  region,  forming  the  funiculus 
uf  Rolando.  Higher  up  this  projection  becomes  even 
more  conspicuous  and  is  known  as  the  tubercle  of 
Rolando.  In  the  region  of  the  pyramidal  decussation 
the  substantia  gelatinosa  of  Rolando  is  separated  from 
the  surface  by  a  longitudinal  mass  of  medullated  fibres 
which  pass  to  the  origin  of  the  fifth  nerve.  This  mass 
of  fibres  is  spoken  of  as  the  ascending  root  of  the 
fifth  nerve. 

188.  The  region  between  the  npper  end 
of  the  pyramidal  cleenssation  and  the 
eouiniencenient  of  the  olives  (Fisf.  140). — In 
this  region  the  central  canal  is  seen  to  lie  more 
posteriorly  corresponding  to  its  gradual  approach 
towards  the  posterior  surface.  The  p3Tamids  oc- 
cupy well  defined  positions  on  the  ventral  side 
of  the  bulb  immediately  abutting  on  the  anterior 
fissure  and  bounded  laterally  by  the  fibres  of  the 
hypoglossal  nerve  coursing  from  the  nucleus  of  the 
twelfth,  across  the  medulla.  There  is  to  be  seen  lying 
in  the  lateral  region  between  the  substantia  o^latinosa 
of  Rolando  and  the  fibres  of  the  twelfth,  a  mass  of 
cells,  which  correspond  to  some  extent  to  the  more 
dorsal  portion  of  the  separated  anterior  horn,  but 
which  in  part  is  to  be  regarded  as  a  new  formation. 


Medulla    Oblongata.  207 

This  mass  of  cells  is  spoken  of  as  the  lateral 
HKc/f'us.  It  is  to  be  noticed  tliat  the  ])Osterior  white 
matter  is  gradually  undergoing  absorption,  being 
invaded  by  the  grey  matter  of  the  corresponding 
nuclei.  The  grey  matter  of  these  nuclei  gradually 
becomes  more  marked,  the  nucleus  of  the  funiculus 
gracilis  early  absorbing  the  white  matter  of  the 
column  and  lying  quite  close  to  the  surface.  The 
nucleus  of  the  funiculus  cuneatus  lies  rather  more 
deeply,  but  is  gradually  invading  the  white  substance. 
The  central  portion  of  the  medidla  becomes  broken 
up,  and  fibres  are  seen  passing  in  an  arched  manner 
from  the  nucleus  gracilis  mainly,  and,  to  some  extent, 
from  the  nucleus  cuneatus  towards  the  middle  line. 
These  arched  fibres  on  reaching  the  middle  line, 
for  the  most  part  bend  longitudinally,  and  thus  form 
a  mass  of  fibres  lying  dorsal  to  the  pyramids,  and 
spoken  of,  higher  up,  as  the  inter-olivary  layer.  This 
decussation  of  fibres  passing  from  the  gracile  and 
cuneate  nuclei  is  sometimes  referred  to  as  the  supei'ior 
or  sensory  decussatior. 

189.  The  region  of  the  lower  portion  ol 
the  olives  (Fig.  141). — A  few  millimetres  higher  up 
than  the  last  section  the  olives  are  seen  to  be  distinctly 
formed,  though  they  have  not  reached  their  greatest  size 
and  though  the  central  canal  is  still  closed.  The  central 
canal  has  at  this  level  approached  yet  more  closely  to 
the  posterior  suiface.  Each  lateral  half  of  the  bulb 
may  be  more  or  less  distinctly  marked  off  into  three 
areas  :  a  median  area  lying  between  the  middle  line 
and  the  roots  of  the  twelfth  nerve  as  they  coui^e  across 
the  bulb  from  the  hypoglossal  nucleus  :  a  lateral  area, 
lying  between  the  roots  of  the  twelfth  and  those  of  the 
eleventh,  which  issue  more  laterally  ;  and  an  area, 
posterior  to  the  eleventh  roots,  which  may  be  called 
the  posterior  area.  The  lateral  nucleus  lies  in  the 
dorsal     portion    of    the     lateral     area.      The    main 


2o8 


Elements  of  Histology. 


mass    of     tlie    olive    lies 
of    the     lateral     area.     Imt 


in    the    ventral     portion 

two    additional     masses, 


S.G. 


XI. 


N  3.  A. 


M.H. 


Fig.  1-tl. — Section  through  the  Medulla  Oblongata  at  level  of  commence- 
ment of  Olives.  {Microphotograph  of  a  specimen  stained  with  aniline 
hlue-hlack.) 

The  central  canal  is  not  yet  opened  out,  and  is  at  level  of  x.s.  a.  :  the  posterior 
grey  matter  is  arranged  iu  three  masses,  >'.  g.,  nucleus  gracilis,  x.c,  nucleus 
ciineatus,  and  s.  g..  the  substantia  gelatinosa  of  Rolando:  with  respect  to 
grey  matter  round  central  canal,  that  at  level  x.  s.  a,  has  cells  forming 
nuclei  of  the  xi,  that  at  level  x.  h.  forming  nuclei  of  xii ;  xi  is  placed 
against  the  line  of  issue  of  the  spinal  accessory,  xii  against  hyi>oglossal ; 
the  grey  matter  lying  slightly  beneath  surface  at  level  l.x.  is  the  lateral 
nucleus;  o,  is  at  level  of  the  twisted  dark  1>and,  the  olive;  the  large  light 
areas  at  level  of  p  are  the  pyramids  :  the  area  more  dorsal  at  level  R.  f.  is  the 
reticular  formation,  in  the  middle  line  of  which  is  the  raphe  (.above  a.  f.  i. 


similar  in  structure  to  the  olive,  may  also  be 
seen,  one  lying  in  the  lateral  area,  dorsal  to  the 
main  olive,  kno^vn  as  the  dorsal  accessory  olives 
and  the   other  lying  in   the   median  area,  separated 


Medulla    Oblongata.  209 

from  the  iimin  olive  by  the  roots  of  the  liypoglossal 
nerve  and  known  as  the  menial  accessory  olive.  The 
more  central  ]»ortion  of  the  section  is  seen  to  be 
broken  np  by  til)res  passing  horizontally,  separating 
others  which  are  proceeding  longitudinally;  and  yet 
other  strands  are  to  be  noticed  intersecting  both  of 
these.  Nerve  cells  are  scattered  through  this  area, 
and  more  conspicuously  in  its  lateral  portions,  and 
these  nerve  cells  with  attendant  neuroglia  may  be 
regarded  as  representing  the  much  ditiiised  grey 
matter  of  the  ventral  horn  which  was  separated  by 
the  decussation  of  the  pyramidal  fibres.  This  broken 
tissue  is  spoken  of  as  the  reticular  formation,  the  more 
lateral  portion,  which  appears  darker  on  account  of  the 
nerve  cells  being  more  numerous,  being  referred  to  as 
the  grey  reticular  formation,  and  the  central  j^art  as  the 
■?r/n"<e  reticular  formation.  In  the  middle  line,  wdi ere 
the  reticular  formations  of  either  side  are  continuous, 
the  decussation  of  the  fibres  coursing  transversely,  and 
the  presence  of  many  fibres  running  in  a  dorso- ventral 
direction,  give  a  somewhat  peculiar  appearance  to 
the  reticular  region.  The  narrow^  intermediate  band 
is  called  the  raphe,  and  it  contains  a  larger  proportion 
of  nerve  cells  than  the  remainder  of  the  median 
reticular  formation.  The  lateral  nucleus  is  still 
prominent  at  this  level,  the  substantia  gelatinosa 
of  Rolando  and  the  ascending  root  of  the  fifth  are 
also  seen.  This  latter  is  gradually  becoming  separated 
from  the  surface  by  a  band  of  fibres  running  longi- 
tudinally but  somewhat  obliquely  wdiicli  represents 
the  commencement  of  the  resti/orm  body  or  inferior 
peduncle  of  the  cerehelhua.  The  longitudinal  fibres 
lying  outside  the  lateral  nucleus  represent  the  upward 
continuation  of  the  direct  cerebellar  tract  and  these 
fibres  gradually  pass  into  the  restiform  body.  Fibres 
are  seen  proceeding  in  a  ventral  direction  from 
the  raphe,  originating  in  part  from  cells  of  the  raphe 
0 


2IO  Elemests  of  Histology. 

but  having  some  connection  proljably  with  the  nuclei 
gracilis  and  cuneatus,  and  these  fibres  passing  from 
the  anterior  fissure  encircle  the  pyramids  and  olives 
and  pass  towards  the  commencing  restiform  bodies. 
These  fibres  are  spoken  of  as  external  arcuate  fibres. 
There  is  to  be  seen  at  about  this  level  for  the  first 
time  a  somewhat  compact  bundle  of  longitudinal  fibres 
lying    between  the   central   canal  and  the  substantia 
jjelatinosa,    though    consideraljlv    nearer   the  former. 
This    bundle    is    surrounded    by    grey    matter,    with 
the    cells  of  which    the    fibres    are    connected.      The 
fibres  of  the  bundle  mainly  pas^s  out   with  the  roots 
of  the  glossopharyngeal  nerve  and  it  therefore  has  been 
called    the    ascending    root    of  the    glossopharyngeal  : 
the  names /'rtSC2C?//?/6'  solitarius  and  respiratory  bundle 
are  sometimes  applied  to  the  same  tract.      In  addition 
to  the  nerve  cells  already  referred  to  other  important 
masses  of  cells  are  now  to  be  seen  distinctly.    («)   llie 
nucleus  of  the  tvnelfth  nerve.     This  consists  of  a  group 
of  nerve  cells  representing,  probably,  the  most  dorsal 
portion  of  the  separated  anterior  horn,  lying  slightly 
ventral  to  the  central  canal.     The  cells  are  multipolar 
and  vary  in  size  from  40-70 yu,  and  the  neuraxons  of 
these  cells,  after  a  somewhat  irregular  course,  become 
the  fibres  of  the  hypoglossal  nerve.     The  fibres  on  each 
side  pass  in  a  ventro-lateral  direction  across  each  half 
of    the    medulla    and    issue    i'rom    the    groove    lying 
immediately  lateral  to  the  pyramids.    (6)   The  nucleus 
of  the    eleventh   nerve.      It  must  be  noted    that    the 
eleventh,  tenth,  and  ninth  nerves  pass  off'  at  different 
levels  from  a  group  of  cells  longitudinally  continuous. 
This  group  of  cells  can  be  spoken  of  as  the  combined 
nucleus  of   the  spinal  accessory  (more   correctly   the 
bulbar  accessory),  the  vagus  and  tlie  glossopharyngeal. 
It  is    not   possible  to  define    precisely    the   divisions 
of    the    nucleus    corresponding    to    each    nerve.      In 
the  region  of  the  medulla    we    are    now    describing, 


Medulla    Oblongata.  211 

liowever,  the  roots  belong  to  the  spinal  accessory  nerve. 
Here  the  nucleus,  consisting  of  a  mass  of  somewhat 
spindle-shaped  cells,  oO-l:0/.i  long  and  12-20/li  wide, 
occupies  a  position  dorsal  to  the  twelfth  nucleus  and 
adjacent  to  the  central  canal.  From  this  nucleus 
tiljres  may  be  traced  passing  laterally  across  each  half 
of  the  medulla,  and  emerging  from  the  l)ulb  between 
the  restiform  body  and  the  olive,  ic)  The  nucleus  of 
the  funiculus  gracilis,  {d)  TJie  nucleus  of  the  funiculus 
cuneatus.  There  may  be  seen  external  to  this  nucleus 
an  isolated  mass  of  cells,  this  is  to  be  regarded  as 
an  accessory  cuneate  nucleus.  (e)  The  lateral 
nucleus. 

190.  The  region  of  the  iiiiddle  of  the  loAver 
half  of  the  fourth  ventricle  (Fig.  142). — At  this 
level  the  central  canal  has  opened  out  into  the  fourth 
ventricle.  This  fourth  ventricle  is  furnished  with  a 
lining  membrane,  consisting  of  columnar  cells  (which 
may  be  ciliated),  resting  upon  neuroglia.  This  lining 
membrane  is  spoken  of  as  the  ependyma.  With  the 
opening  out  of  the  central  canal  the  gracile  and  cuneate 
nuclei  have  retreated  from  their  median  position  and 
come  to  lie  in  the  dorso-lateral  region.  The  two  gracile 
nuclei  therefore  are  separated  from  one  another  by  the 
width  of  the  fourth  ventricle.  The  nucleus  of  the 
twelfth  nerve  lies  now  in  the  median  position  at  the 
dorsal  surface,  and  in  this  locality  a  slight  bulging 
into  the  ventricle  exists  which  corresponds  to  the 
funiculus  teres.  Lateral  to  the  nucleus  of  the  twelfth 
lies  the  combined  nucleus  of  the  eleventh,  tenth  and 
ninth,  here  corresponding  to  the  vagus  nerve.  The 
restiform  Vjody  has  increased  in  size  and  has  now 
largely  absorlied  the  direct  cerebellar  tract.  The 
olives  are  also  much  more  prominent,  and  have 
here  reached  their  full  development.  These  bodies 
each  consist  of  a  lamina  of  grey  matter  folded  back 
upon    itself,    enclosing    a    space    filled    with    white 


212 


Elements  of  Histology. 


matter.  The  convex  portion  of  the  fold  corresponds  to 
the  external  protuberance.  This  lamina  has,  in  addition 
to  the   main    fold,    numerous   secondary   longitudinal 


N  V. 


N  H 
R. 


A.V. 


"\  X. 


\ 


■(,? 


'V-^--^' 


Xli 


Fig.  142. — Section  throufrli  the  Medulla  Oblongata  at  level  of  middle  of 
Olives.     {Microphotograph  of  a  specirueii  stained  rvith  aniline  llue-black.) 

B  lies  over  the  raphe  ;  a  mass  of  grey  matter  just  beneath  x.  h.  is  nucleus  of  the 
xiith,  beneath  y.  v.  is  nucleus  of  the  xth  :  beneath  x.  g.  and  y.  c.  are  the 
nuclei  of  the  fasciculi  gracilis  and  cuneatus  ;  c.  k.  lies  atrainst  the  light 
mass  of  the  restiform  body,  slightly  deeper  at  level  a.  v,  is  the  ascending  vth  ; 
X  is  placed  against  the  issuing  x.,  and  running  down  towards  xii,  from 
nucleus  of  the  xiith  are  the  fibres  of  the  xiith  :  y.  a.  is  against  grey  matter 
forming  the  nuclei  of  the  external  areiform  fibres  :  the  olive  is  seen  lateral 
to  the  roots  of  xiith  as  a  deeply  stained  undulating  band  ;  a  part  is  separated 
on  the  dorsal  side  (the  dorsal  olive)  and  a  small  part  lies  on  median  side  of 
roots  of  xiith  (the  median  accessory  olive  i ;  at  level  of  c.  R.and  immediately 
beneath  f.s.  is  a  light  circular  area,  the  fasciculus  solitarius;  the  grey 
matter  lying  at  level  of  x  and  a  little  below  the  surface  is  the  lateral  nucleus. 


folds,  so  that  in  transverse  section  it  presents  the 
appearance  of  a  Avavy  Ijand  of  grey  matter  passing 
from    the   formatio    reticularis    towards   the    surface, 


Med ulla    Oblonga  ta.  213 

and  then  arching  back  it  continues  its  wavy  course 
towards  the  region  from  which  it  started.  Inter- 
nally there  pass  into  the  interior  of  the  olive  tracts 
of  white  fibres  which  radiate  outwards  towards  the 
concave  surface  of  the  lamina.  The  lamina  itself  is 
composed  largely  of  neuroglia,  broken  by  nerve  fibres 
passing  across,  there  are  also  present  many  multi- 
polar nerve  cells.  These  cells  possess  axis-cylinder 
processes  which  possibly  pass  down  into  lateral 
columns  of  the  cord  and  become  connected  with 
motor  cells  in  the  grey  matter.  They  are  themselves 
connected  with  nerve  fibres  which,  springing  originally 
from  the  cells  of  Purkinje  in  the  cerebellum,  course 
through  the  restiform  body  and,  becoming  cerebello- 
olivary  fibres  in  the  medulla,  pass  across  the  opposite 
olive.  It  may  also  be  that  the  olives  are  connected 
by  longitudinal  fibres  with  the  cerebral  hemispheres. 

It  is  possible  to  classify  to  some  extent  the 
numerous  fibres  passing  transversely  across  the 
medulla  in  this  region. 

Somewhat  lower  than  the  transverse  section 
we  are  at  present  considering  were  decussating 
fibres  from  the  gracile  and  cuneate  nuclei,  called 
internal  arcuate  fibres,  forming  the  inter-olivary  layer. 
With  the  development  of  the  restiform  body  and  the 
olives,  other  fibres  proceeding  transversely  become 
prominent.  The  external  arcuate  fibres  may  be 
held  to  comprise  three  minor  groups.  («)  Those 
passing  from  the  raphe  and  encircling  the  pyra- 
mids and  olives.  Amongst  these  fibres  in  the 
upper  part  of  the  bulb  are  a  mass  of  nerve  cells 
known  as  the  nucleus  arciformis.  (6)  Fibres  passing 
from  the  lateral  tract  into  the  restiform  body.  These 
are  largely  the  more  superficial  of  the  fibres  of  the 
direct  cerebellar  tract.  (c)  Fibres  passing  dorsally 
from  the  gracile  and  cuneate  nuclei  to  the  restiform 
body  of  the  same  side.     These  fibres  are  also  spoken 


2  14  Elements  of  Histology. 

of  as  superficial  dorsal  arcuate  fibres.  In  adrlition 
to  the  so-called  arcuate  fibres  there  are  other  fibres 
which  have  a  somewhat  arched  course,  but  which  are 
best  separated  into  a  distinct  class,  and  spoken  of  as 
cerehello- olivary  fibres.  These  include  a  majority  of 
the  fibres  forming  the  restiform  body.  They  pass 
from  the  restiform  body  either  laterally  to  the  ascend- 
ing root  of  the  fifth,  or  to  some  extent  intersecting  it, 
and  proceed  towards  the  dorsal  lamina  of  the  olive. 
Most  of  the  fibres  then  penetrate  the  grey  matter 
(a  few  perhaps  becoming  lost  therein),  and  passing 
into  the  white  core  of  the  olive  emerge  at  the  olivary 
peduncle  and  proceed  to  the  raphe.  The  more 
dorsal  of  these  fibres  passing  from  the  restiform  body 
do  not  intersect  the  olive  ;  the  more  ventral  pass 
round  the  olive  (and  are  hence  regarded  by  some  as 
external  arcuate  fibres),  and  entering  between  the 
olive  and  pyramid  pass  to  the  raphe.  Having 
crossed  the  raphe  these  fibres  either  bend  longitudi- 
nally or  pass  to  the  olivary  grey  matter.  The 
longitudinal  fibres  Ivino^  between  the  olives  in  the 
ventral  portion  of  the  formatio  reticularis  are  known 
as  the  inter-olivary  layer.  This  diffuse  column  of 
fibres  becomes  more  distinct  higher  up,  and  is  then 
known  as  the  fillet  or  lemniscus.  In  the  posterior 
part  of  the  formatio  reticularis  near  the  raphe,  a 
fasciculus  of  longitudinal  fibres  is  gradually  becoming 
more  distinct.  This  is  known  as  the  posterior  longi- 
tudinal bundle,  and  is  to  be  regarded  as  representing 
a  part  of  the  anterior  or  ventral  column  of  the  cord. 
The  hypoglossal  nucleus  lies  now  on  the  floor  of 
the  ventricle,  and  external  to  it  lies  the  nucleus  oj 
the  vagus.  The  cells  forming  this  nucleus  may  be 
divided  into  two  groups,  a  more  median  and  a  more 
lateral.  The  median  group  consists  of  the  larger  cells. 
In  addition  to  this  superficial  nucleus  there  lies  in 
the   formatio  reticularis,  midway  between  the  fibres 


Med  ulla    Obl onga  ta.  215 

of  the  twelfth  aiul  clcveiitli  nerves,  a  second  nucleus 
known  as  the  nucleus  amhijaus  or  motor  nucleus  oj 
the  tentli.  Fibres  from  this  nucleus  pass  dorsally  to- 
wards the  main  vagus  nucleus,  and  issue  with  the 
vagus  roots.  Fibres  from  the  fasciculus  solitarius 
also  pass  out  with  the  vagus.  The  vagus  fibres  thus 
have  three  centres  of  origin. 

A  section  taken  somewhav  higher  than  that  just 
considered  would  show  the  issue  of  the  glosso- 
pharyngeal nerve.  A  majority  of  the  fibres  of 
the  fasciculus  solitarius  pass  out  with  the  glosso- 
pharyngeal, running  first  towards  the  main  nucleus, 
and  then  turning  back  and  coursing  with  the  fibres 
of  the  ninth  nerve.  There  are  also  to  be  seen  at 
this  level,  rather  more  distinctly  than  in  the  lower 
section,  lying  somewhat  external  to  the  fasciculus 
solitarius,  and  near  to  the  grey  matter  corresponding 
to  the  nucleus  gracilis,  some  scattered  longitudinal 
bundles  of  fibres,  which  are  connected  with  the 
auditory  nerve,  and  are  known  as  the  asceruJimj  root 
of  the  eighth. 


2l6 


CHAPTER     XVIII. 

CONTINUATION  OF  THE  MEDULLA  OBLONGATA 
THROUGH  THE  PONS  VAROLII  AND  THE  REGION  OF 

THE  CRURA. 

191.  Tliereg:ioii  of  the  iiii<l<1loof  the  fourth 
veiitriele  (Fig.14.3). — Adorso-ventral  section  passing 
through  that  part  of  the  fourth  ventricle  across  which 
the  striae  acusticse  course  would  be  somewhat  below 
the  precise  middle  of  the  ventricle,  but  may  be  con- 
veniently considered  first.  Such  a  section  would  not 
involve  the  pons  varolii  and  would  probably  just 
miss  the  exit  of  the  sixth  nerve.  In  such  a  section 
the  upper  part  of  the  diminishing  olive  would  be 
seen  still.  The  formatio  reticularis  occupies  the 
median  portion  of  each  half,  and,  laterally,  the  resti- 
form  body  is  here  at  its  maximal  size.  Coursing 
ventro-laterally  with  respect  to  the  restiform  body 
are  seen  the  higher  roots  of  the  ninth  nerve  ;  on  the 
median  side  of  this  there  appears  the  ascending  root 
of  the  fifth.  On  the  median  side  of  the  dorsal  portion 
of  the  restiform  body  are  seen  longitudinal  fibres 
belonging  to  the  ascending  root  of  the  eighth  nerve, 
and  lying  somewhat  dorsal  to  this  are  nerve  cells 
belonging  to  the  same  nerve.  The  dorsal  edge  of 
the  section  appears  to  be  composed  of  transverse 
dbres  coursing  from  the  raphe  round  the  restiform 
body  and  directed  towards  the  exit  of  the  eighth 
nerve.     These  are  the  stance  aciisticd'. 

Lying  on  the  ventrolateral   side  of  the  restiform 


Medulla    Oblongata. 


2  I  7 


body  is  a  mass  of  nerve  cells  connected  with  the 
fibres  of  the  acoustic  nerve  and  called  the  ventral 
ganglion  of  the  eighth.  A  section  taken  slightly 
higher  would  involve  the  pons  and  show  some  slight 


Fig.  143.— Part  of  a  transverse  section  of  the  Medulla  Oblongata  through 
the  exit  of  the  Auditory  Nerve.  (Micropliotograph  of  a  IVeigert-Fal 
specimen.) 

The  section  is  slightly  obliiiiie,  ;uid  lience  at  the  level  d  the  cochlear  nerve 
(N.  c.)  is  seen  dividing  into  ascending  (the  more  median)  and  descending  (the 
more  lateral)  divisions.  The  half-moon-shaped  mass,  dark  in  C(dour  at  level 
C.  E.,  is  the  restiform  body.  The  dark  mass  lying  in  centre  of  the  photograph 
at  level  of  v  is  the  ascending  root  of  the  fifth  nerve.  The  lighter  substance 
at  level  of  D  lying  mainly  on  inner  side  of  the  cochlear  nerve  is  the  ventral 
ganglion,  the  cells  of  the  tulierculum  acusticum  are  in  the  lighter  substance, 
rather  above  the  level  of  D,  and  lateral  to  the  cochlear  nerve.  s.R;,  lateral 
portion  of  stri®  acusticae. 

changes  when  compared  with  the  section  just  described. 
The  most  conspicuous  difference  in  the  higher  section 
consists  in  the  presence  of  a  prominent  mass  of 
transverse  fibres  passing  across  on  the  ventral  aspect 


2iS  ELEME^rs  OF  Histology. 

and  breaking  up  the  pyramids  into  smaller  bundles. 
The  auditory  nerve  is  to  be  seen  issuing  as  before,  and 
on  the  median  side  of  tlie  eighth  a  second  nerve,  the 
seventh,  passes  out.  It  must  be  remembered  that 
neither  the  sixth  nor  the  seventh  nerves  pass  by  direct 
dorso-ventral  courses  outwards.  The  seventh  nerve 
originates  from  a  nucleus  lying  in  the  formatio 
reticularis  midway  between  the  ventral  acoustic 
nucleus  and  the  raphe,  and  at  about  the  same  level 
as  the  nucleus.  The  libres  from  the  facial  nucleus  at 
first  pass  dorsally  and  then  turn  longitudinally  and 
pass  for  a  short  distance  upwards,  becoming  involved 
in  the  nucleus  of  the  sixth.  After  a  short  upward 
course  they  turn  back  again  towards  the  lower  region 
of  the  bulb,  and,  takimj  o^raduallv  a  more  ventral 
direction,  finallv  emerije  near  the  exit  of  the  eio'hth 
nerve.  There  also  pass  out  with  the  facial  nerve 
fibres  derived  from  the  hinder  portion  of  the  nucleus 
of  the  third  nerve.  These  fibres  sujDply  the  orbicu- 
laris palpebrarum  and  frontalis  muscles.  The  nerxe 
cells  composing  the  nucleus  of  the  seventh  are  about 
40-60/i  in  size,  their  neuraxons  are  directed  dorsally 
to  form  the  nerve  fibres  of  the  facial  nerve. 

A  mass  of  grey  matter  is  also  seen  lying  slightly 
median,  and  ^■entral  to  the  seventh  nucleus.  This 
mass  of  grey  matter  contains  nerve  cells,  and  is  known 
as  the  superior  or  little  olive.  This,  in  adults,  is  about 
4-5  mm.  in  lengtli,  but  is  better  developed  in  lower 
animals.  The  cells  are  similar  to  those  of  the  olive, 
about  30— tO/z  in  diameter,  with  neuraxons  and  much- 
branching  dendrites.  Another  mass  of  cells  is  to 
be  made  out  on  the  ventro-median  aspect  of  the 
superior  olive.  This  is  known  as  the  trapezoid 
nucleus.  Fibres  may  be  seen  proceeding  from  the 
ventral  nucleus  of  the  eighth,  and  passing  on  the 
ventral  side  of  the  superior  olive  and  the  trapezoid 
nucleus.       These    fibres    constitute     the    trapezium., 


Med  ulla    Obl onga  ta.  219 

and  form  the   most   tlorsal  portion  of  the  transverse 
fibres  of  the  pons. 

The  connection  of  tlie  auditory  nerve  with  its 
different  origins  is  now  to  be  described.  There  are 
three  main  nuclei  from  which  origin  takes  place  : — 
(a)  the  ventral  or  accessory  nucleus  lying  near  the 
place  of  exit  of  the  nerve,  and,  from  its  resemblance 
to  a  spinal  ganglion^  sometimes  called  the  acoustic 
ganylion  ;  (b)  a  mass  of  cells  lying  on  the  floor  of  the 
fourth  ventricle,  midway  between  the  restiform  body 
and  the  median  furrow,  called  the  dorsal  median 
nucleus ;  and  (c)  a  mass  of  cells  lying  near  the 
ascending  root  of  the  eighth,  between  the  median 
nucleus  and  the  restiform  body,  but  somewhat  deeper 
than'  the  former,  called  the  dorso-lateral  nucleus  or 
nucleus  of  Deiters.  The  ventral  nucleus  is  really 
divisible  into  two  ;  a  more  lateral  portion  and  the 
main  ventral  nucleus.  The  lateral  portion  forms  the 
tuherculum  acusticum.  The  eighth  nerve  can  be 
seen  to  consist  of  two  parts,  one  part  passes  to  the 
median  side  of  the  restiform  body,  the  other  to  the 
lateral  aspect.  The  former  is  called  the  vestihidar 
nerve,  and  the  latter  the  cochlear  nerve,  corresponding 
to  the  destination  of  these  two  divisions.  The 
cochlear  nerve  has  finer  fibres  than  the  vestibular, 
the  fibres  of  the  former  being  1-2*5^,  those  of  the 
latter  2-4^,  The  fibres  of  both  nerves  divide,  like 
a  spinal  posterior  root  fibre,  into  an  ascending  and 
descending  branch  after  enterins;  the  medulla.  The 
ascending  branches  of  the  cochlear  nerve  pass  to 
the  ventral  nucleus,  the  descending  branches  to  both 
the  tuberculum  acusticum  and  the  ventral  nucleus. 
From  the  ventral  nucleus  fibres  pass  as  already 
stated  into  the  trapezium  and  become  connected  in 
part  with  the  cells  of  the  superior  olive  and  the 
nucleus  trapezoides.  The  cells  of  the  tuberculum 
acusticum,  and  partly  also  those  of  the  ventral  nucleus, 


220 


Elements  of  Histology. 


originate  the    fibres    composing   the    strua    acusticce. 
(Fig.  152.)     The  fibres,  therefore,  coursing  round  the 


'^m 


FiK.   144. 


-.•Section  through   the   .Sixth    Nucleus  aud   Genu    of    Seventh. 
(Pliotograph  of  a  Weigert-Pal  preparation.) 


The  lower  half  constitutes  the  hulk  of  the  pons  proper,  with  laterally  the  middle 
peduncles;  the  two  syuiinetriCHl  dark  masses  at  level  F  are  the  longitudinal 
fibres  of  tbe  fillet  ;  on  the  left  side  and  lateral  to  the  fillet  is  seen  a  darkish 
mass  with  a  lighter  centre,  the  .-uperior  olive.  The  floor  of  the  fourth  ven- 
tricle forms  tbe  median  part  of  the  upper  edge,  two  symmetrical  light  masses 
beneath  vi  are  the  vith  nuclei.  Fibres  from  the  inner  side  are  seen  passing 
downwards  near  the  middle  line,  these  are  the  fibres  of  the  vith.  The 
fibres  of  the  viith  are  seen  passing  apparently  from  the  outer  side  of  the 
vith  nucleus  on  the  left  side.  The  nucleus  of  the  viith  lies  on  dorsal  side  of 
the  olive.  The  darkest  tissue  Ijing  beneath  v  and  at  level  a  constitutes  the 
somewhat  scattered  fibres  of  the  ascending  root  of  vich.  The  genu  of  the 
viith  is  between  the  nucleus  of  vith  and  the  median  sulcus  and  Is  better 
seen  in  the  enlargement  of  this  region.    (Pig.  145). 


restiform  body,  though  apparently  the  continuation  of 
the  cochlear  nerve,  are  really  the  neuraxons  of  cells  of 


Med  ul la    Obl onga  ta  . 


221 


the  tuberculuni  acusticum  and  ventral  nucleus,  wliich 
are  connected  with  the  terminal  arborescences  of 
fibres  composing  the  cochlear  nerve.     The  vestibular 

N.A.  G.F. 


F.N.  i 


A  N 


Fig.  145.— Section  througli  the  Nucleus  of  the  Sixth,  being  a  part  more 
highly  magnified  of  Fig.  144.  {Microphotograph  of  a  Weigert-Pal 
specimen.) 

The  letters  x.a.,  g.  f..  aud  r.  lie  over  the  cavity  of  the  fourth  ventricle,  r  lies 
ahove  the  raphe.  A  dark  circular  patch  a  little  below  g.  f.  corresponds  to 
the  genu  of  tlie  viith  nerve,  x.  a.  lies  above  a  circular  light  area  wlaich  is 
the  nucleus  of  tlie  vith.  F.  N.  lies  against  the  lower  end  of  a  darkly  stained 
mass  of  fibres  which  can  he  dimly  traced  round  the  nucleus  of  the  vith 
towards  the  outer  side  of  the  genu  of  vii.  This  corresponds  to  the  facial 
nerve  just  before  it  issues  from  the  medulla.  Fibres  are  seen  passing  from 
inner  side  of  vith  nucleus  towards  a.  n.,  the  fibres  of  the  vith  nerve. 


nerve  fibres  also  divide, 


ascending  and  descending 
branches   become 


on  entering   the   bulb,  into 

branches.     These  different 

connected    with   the    cells    of    the 


2  22  ElEMF.XTS    of   HlSTOLOGV. 

clorso-inedian  nucleus,  Deiters's  nucleus,  and  the 
cells  around  the  ascending  root  of  the  eighth.  As 
regards  the  further  course  of  the  stria?  acusticse,  these 
bundles  show  many  fibres  passing  vertically  into 
the  central  mass  of  the  bulb  or  the  tegmentum^ 
as  it  is  termed ;  other  fibres  of  the  striES  acusticse 
decussate  at  the  raphe,  some  pass  thence  towards 
the  superior  olive  and  turn  longitudinally,  others 
pass   towards  the   restiform   body. 

192.  Region  of  iiiicleiis  of  seveiitli  nerve. 
The  nucleus  of  the  seventh  extends  towards  the  mid- 
brain, almost  to  the  upper  limit  of  the  nucleus  of  the 
sixth.  A  section  taken  through  the  junction  of  the 
upper  and  middle  thirds  of  the  fourth  ventricle  would 
pass  through  Vjoth  these  nuclei,  showing  the  appearance 
seen  in  Fig.  14  4-.  The  fibres  here  are  seen  passing 
from  the  nucleus  of  the  seventh  towards  that  of 
the  sixth,  which  is  seen  on  the  floor  of  the  fourth 
v^entricle.  Towards  the  inner  side  of  this  a  more  or 
less  prominent  mass  of  fibres  of  the  seventh  turn 
longitudinally,  forming  the  genu  of  the  seventh 
(Fig.  145),  and  there  are  seen  laterally  fibres  about 
to  pass  out  of  the  bulb,  belonging  to  this  same  nerve. 
The  nucleus  of  the  sixth  or  abducens  nerve  consists 
of  multipolar  cells,  about  40-50  fx  in  diameter.  The 
neuraxons  of  these  cells  pass  from  the  median  side 
ventrally  towards  the  pons  and  run  through  this 
Avitli  an  oblique  backward  course  so  as  to  issue  at 
the  lower  edge  of  the  pons  in  line  with  the  roots 
of  the  twelfth.  The  nucleus  is  connected  with  the 
superior  olive  by  a  bundle  of  fibres,  which  is  called 
the  pedicle  of  the  superior  olive.  Other  connections 
exist  with  the  pyramidal  bundles  and  the  posterior 
longitudinal  bundle. 

193.  The  region  of  the  upper  end  of  the 
fourth  ventricle.  (Fig.  146.) — A  section  through 
the    nuclei    of    the     fifth    nerve     would     show    the 


Med  ul  la    Ob  long  a  ta  . 


22 


characters  uf  a  transverse  section  in  this  region.  The 
origins  of  the  fifth  seen  in  this  section  consist  of 
two  more  or  less  distinct  masses  of  cells,  the  outer 
being    described    as   the    sensory    nucleus,  the    inner 

Vs 


Fit 


140. — SectioL  chrough  the  Nucleus  of  the  Fifth  Nerve. 
graph  of  a  Weigert-Fal  preparation.) 


{Microphofo- 


Below  is  seen  a  small  part  of  the  pons  proper,  and  at  p  are  fibres  passing  circuni- 
ferentially  towards  tbe  pons.  At  level  F  is  a  dark  mass  on  left  side  of 
middle  line  of  section,  the  fillet  (above  this  and  near  the  centre  of  the  micro- 
pbotoeraph)  at  level  s.  o.  is  tbe  superior  olive.  At  level  x.  and  beneath  vm. 
and  vs.  are  tbe  two  nuclei  of  the  vth  ;  from  these  and  between  these,  at  level 
T,  are  seen  fibres  passing  downwards  towards  the  pons  fibres— these  form  the 
vth  nerve. 


as  the  motor  nucleus.  From  these  masses  of  cells 
nerve  fibres  are  seen  to  pass  in  a  ventro-lateral 
direction  to  the  fifth  nerve.  The  more  exact  origin 
of  this  nerve   may  be  now  referred  to.     In  the  first 


2  24  Elements  of  Histology, 

place  the  nerve  consists  of  two  parts,  the  motor  and 
the  sensory  divisions.  Tlie  sensory  divisioit  proceeds 
from  the  Gasserian  ganglion,  and,  on  reaching  the 
deeper  layers  of  the  pons,  the  different  fibres  divide  into 
ascending  and  descending  portions,  like  an  ordinary 
sensory  nerve.  The  descending  portions  form  a 
bundle  of  fibres,  the  so-called  ascending  root  of  the 
fifth,  which  has  been  referred  to  in  most  of  the  regions 
already  described.  This  can  be  traced  down  distinctly 
as  far  as  the  pyramidal  decussation.  The  bundle 
diminishes  in  amount  on  tracing  it  downwards, 
and  is  always  associated  with  a  mass  of  grey  matter 
lying  on  the  median  side,  the  substantia  gelatinosa. 
In  this  substantia  gelatinosa  are  cells  round  which 
the  fibres  of  the  ''  ascending  "  root  form  arborescences. 
At  the  level  of  the  exit  of  the  fifth  these  cells  of 
the  substantia  gelatinosa  are  more  evident,  and  are 
referred  to  as  the  chief  sensory  nucleus.  The 
ascending  branches  of  the  bifurcating  sensory  root 
])ecome  connected  with  the  cells  of  the  chief  nucleus. 
From  the  cells  lying  in  the  substantia  gelatinosa 
against  the  "  ascending  "  fifth  along  its  whole  length 
there  pass,  towards  the  middle  line,  arched  fibres, 
which  cross  the  raphe,  then  become  longitudinal 
in  their  course  and  enter  the  fillet.  On  their 
way  towards  the  upper  part  of  the  brain  these  fillet 
fibres  of  the  fifth  give  off  numerous  collaterals  which 
are  connected  with  cells  in  the  reticular  formation. 
The  motor  root  sjDrings  from  the  motor  nucleus.  This 
occupies  the  position  somewhat  of  an  upward  con- 
tinuation of  the  seventh  nucleus.  It  consists  of  large 
multipolar  cells  (50-70/.f)  having,  however,  blunt, 
unbranched  processes.  The  fibres  forming  the  motor 
root  are  partially  decussated,  so  that  the  root  on  one 
side  is  composed  of  fibres  derived  from  the  motor 
nuclei  of  both  sides.  There  are  connections  between 
the  motor  and  sensory  nuclei  which  may  furnish  the 


Med  ul  l  a    Ob  long  a  ta.  225 

path  for  reriex  masticatory  action.  There  must 
also  exist  connections  with  fibres  of  the  pyramidal 
system.  Passing  dorsally  between  the  two  nuclei 
are  seen  fibres  which  turn  longitudinally  and  form 
a  small  tract  traceable,  upwards,  about  as  far  as  the 
anterior  corpora  quadiigemina.  This  is  known  as  the 
"  descending  "  or  cerebral  root  of  the  fifth.  It  will 
perhaps  be  well  to  describe  its  course  here.  In 
the  region  of  the  posterior  corpora  quadrigemina  it 
lies  near  the  dorsal  angle  of  the  superior  cerebellar 
peduncle  and  dorso  lateral  to  the  outer  angle  of  the 
posterior  longitudinal  bundle.  It  is  separated  from 
this  bundle  by  a  mass  of  pigmented  cells,  known 
as  the  substantia  fer rug inea  (Fig.  147).  The  "des- 
cending "  root  can  be  traced  upwards  as  a  bundle 
of  large  fibres  aoainst  which  lies  scattered  round  or 
spindle-shaped  nerve  cells,  less  deeply  pigmented  than 
those  of  the  substantia  ferruginea.  Passing  to  the 
level  of  the  anterior  corpora  quadrigemina,  the  root 
can  be  seen  for  some  distance,  lying  at  the  edge  of 
the  grey  matter  surrounding  the  Sylvian  aqueduct 
and  near  the  upper  end  of  the  anterior  corpora 
quadrigemina  it  becomes  lost.  Returning  to  other 
structures  seen  at  the  level  of  the  exit  of  the  fifth 
nerve,  it  will  be  well  to  refer  to  the  appearance 
now    presented   by  the  fillet. 

In  the  middle  of  the  fourth  ventricle  the  fillet 
consists  of  a  mass  of  longitudinal  fibres  lying  on  either 
side  near  the  middle  line  and  separating  the  formatio 
reticularis  from  the  transverse  fibres  of  the  pons. 
In  the  sub-pontine  region  the  fillet  fibres  lie  between 
the  olives,  forming  the  inter  olivary  layer.  In  the 
upper  portion  of  the  fourth  ventricle  the  fillet  on 
either  side  divides  into  two  masses,  one  part  lying 
between  the  superior  olive  and  the  middle  line, 
forming  the  median  fillet,  the  other  lying  dorsal  to 
the  superior  olive  and  known  as  the  lateral  fillet. 
p 


2  26  Elements  of  Histology. 

The  fibres  of  the  median  fillet  are  derived  originally 
from  the  nuclei  of  the  funiculi  gracilis  and  cuneatus 
as  well  as  from  the  nuclei  of  the  vagus,  glasso- 
pharviigeal.  ami  ^■r^tilal^;^l■  nerve.  The  lateral  fillet 
probably  originates  (Ij  from  fibres  of  the  trapezium, 
passing  from  the  ventral  acoustic  ganglion  of  the 
ojiposite  side  and,  therefore,  connected  with  the 
cochlear  root  of  the  eighth;  (2)  from  the  superior 
olives  on  both  sides  and,  higher  ui>,  from  a  collection  of 
cells  in  the  course  of  the  lateral  fillet,  known  as  the 
nucleus  qftJie  lateral jillet j  (3)  from  longitudinal  fibres 
lying  against  the  superior  olive,  which  increase  in 
ntmiber  on  proceeding  upwards;  (4)  possibly,  from 
fibres  derived  from  the  striae  acusticae,  which  have 
passed  ventrally  into  the  tegmentum  and  turned  into 
the  tract  of  the"^ fillet. 

The  ^jo/is  proper  is  made  up  of  numbers  of 
transverse  fibres  passing  laterally  from  the  middle 
peduncles  of  the  cerebellum  on  one  side  to  that 
on  the  other.  In  crossing  ventrally  upon  what  is  the 
continuation  of  the  substance  of  the  bulb  these  fibres 
divide  the  pyramids  into  groups  of  longitudinal  fibres. 
The  more  dorsal  of  these  transverse  fibres  (those 
lying  immediately  adjacent  to  the  upward  con- 
tinuation of  the  formatio  reticularis)  are  known 
by  the  special  name  of  the  trapezium.  Amongst  the 
transverse  fibres  of  the  pons  are  numerous  scattered 
masses  of  grev  matter  with  which  manv  of  the 
loncjitudinal  fibres  become  connected. 

194.  The  reg^ioii  of  tlie  posterior  coi*pora 
qiiadri^eiiiina  and  upper  part  of  tlie  poii^>. 
— The  first  section  taken  is  immediately  below  (distal) 
the  posterior  corpora  quadrigemina.  The  fourth 
ventricle  has  here  narrowed  to  form  the  commence- 
ment of  the  aqueduct  of  Sylvius.  Surrounding  the 
channel  is  the  ependyma  enveloped  on  all  sides  by 
a   considerable    thickness    of  ^rex    matter.     In  that 


Med ulla    Obl onga  ta . 


227 


portion   lying  on  the  ventral  side  maybe  seen  masses 
of  cells  foi-mini:  the   commencement  of  the  nuclei  of 


S.C.P    IV.         I.     IV.  V.  S.C.P. 


P.L.B 


L.F 


M.F 


Fig.  147. — Section  throu<:li  the  Pons  Varolii  immediately  below  the 
Posterior  Corpora  Quadrigemina.  {Fhotograph  of  a  U'eigert-Pal 
specimen.) 

The  main  mass  of  the  section  forms  the  fibre?  of  the  pons  (P).  The  two  large 
dark  masses  in  the  upiier  part  (under  >s.  c.  p. »,  the  lower  ends  meeting  in 
middle  line,  are  the  superior  cerebellar  peduncles  or  lirachia  conjunctiva. 
The  area  included  between  their  lower  halves  forms  tbe  teirmentum.  Tbe 
iiuadrangular  space  lielow  i  is  the  Sylvian  aiiueduct.  Decussating  in  the 
valve  of  Vieussens  above  are  seen  fibres  of  the  ivth  nerve,  the  two  small  dark 
masses  below  iv  being  the  main  trunks  lying  obli.iuely.  Lying  a  short 
distance  below  the  aqueduct  at  p.  l.  b.  are  two  dark  comma-shaped  masses, 
the  posterior  longitudinal  bundles.  The  twu  elongated  dark  masses  one 
lying  against  l.  f..  the  ntlier  passing  l)etween  the  pons  fibres  and  the  superior 
cerebellar  peduncles  opposite  M.  f.  are  the  lateral  and  median  fillets.  The 
darkish  mass  lying  below  v,  just  on  the  median  side  of  the  upper  part  of 
the  peduncle  is  the  descending  root  df  vth. 

the  fourth  nerve.     Lying  again   ventral  to  thi.s  grey 
matter  are  two  prominent  longitudinal  bundles  on 


2  28  Elements  of  Histology. 

either  side  of  the  middle  Une,  tapering   towards  the 
lateral  region.     These  are  the   posterior  longitudinal 
bundles.     Near  the     lateral    tapering    end    of    these 
bundles  may  be  seen  the  desceitdiag   root  of  the  fifth 
nerve,    separated    by    a    mass  of  cells    forming    the 
substantia  femiginea    or  locus  cceruleus.      Lying  to 
the    median  side    of   the    root    of  the    fifth  may    be 
seen  bundles  of  white  fibres  pa^^sing  into  the  superior 
nieduUary   velum  or   valve  of  Vieussens,  decussating 
here   (Fig.    1J:7)  and  issuing  literally   as  the  fourth 
nerve.     Lying  again  ventrally  and  laterally    to  the 
posterior    longitudinal  bundles,    and    separated  from 
them  by    what    is  an    upward    continuation    of    the 
reticular   formation,     are    the    upward    prolongations 
of     the    superior     cerebellar    peduncles    or    brachia 
conjunctiva.      There  at    the    level    of    the    nuclei    of 
the  fifth  nerve,  in  section,  two  semicircular   masses 
lie    immediately  lateral    to    the  side    of    the    fourth 
ventricle.       Passing    upwards,    they    gradually    take 
a    more    venti-al    position    till,     as     in    the    present 
section,  they  commence  to   fuse  in  the  middle  line. 
At  a  short  distance  externally  and  ventrally  to  the 
superior    cerebellar    peduncle    is    seen    another  band 
of  longitudinal  fibres.      This  band   is  of  considerable 
thickness  between  the  peduncle  and  the  lateral  surface, 
then  passing    ventrally    it    narrows    somewhat^    and 
widens  again  to  a  fairly  broad  band  lying  on  the  dorsal 
side  of  the   pons  proper.      This  is  the  fillet  or  lem- 
niscus,  the  lateral  portion  witli   nerve   cells   forming 
its  nucleus  being  the  lateral  fillet,  that  portion    lying 
adjacent  to  the  pons  being  the  median  fillet.    Ventrally 
to  this  again   is   the  substance    of  the    pons   proper, 
having  the  characters  described  in  ^  193. 

A  section  slightly  higher  would  pass  through  the 
posterior  corpora  quadrigemina.  Here,  there  would 
appear  two  protuberances,  dorso  -  laterally  to  the 
aqueduct.      The   lateral  fillet  forms  connections  with 


Medulla    Oblongata.  229 

these  bodies.  Tlie  pons  pioper  is  here  soinewliat 
smaller,  the  up])er  limit  being  appruuched.  The  two 
superior  cerebellar  peduncles  gradually  lessen  in  width, 
their  lateral  extensions  disappearing  by  degrees.  The 
nucleus  of  the  fourth  nerve  consists  of  a  mass  of  large 
multipolar  cells  lying  in  the  grey  matter  on  the 
ventral  side  of  the  aqueduct  and  near  the  middle  line, 
and  reaching  from  the  upper  to  almost  the  lower 
extremity  of  the  posterior  corpora  quadrigemina. 
The  fibres  from  these  cells  take  a  somewhat  oblique 
backward  course  to  the  lower  limit  of  the  posterior 
corpora  quadrigemina  where  they  decussate,  as  already 
described.  In  the  region  of  the  posterior  cor[)ora 
quadrigemina  the  posterior  longitudinal  bundle  is 
very  prominent.  The  basal  ends  of  the  ependyma 
lining  the  aqueduct  are  frequently  continued  into  a 
set  of  fine  fibres  which  pass  through  the  grey  matter 
(and  even  beyond)  and  give  a  radially  striated 
appearance  to  the  region  adjacent  to  the  aqueduct. 

195.  The  region  ot  llie  anterior  eorpora 
quadrigemina  and  the  cinra  eei  ebri. — 
At  this  level  (Fig.  148)  the  pons  has  disappeared, 
and  its  position  is  occupied  by  two  well-marked 
protuberances  on  the  ventral  side,  spoken  of  as 
the  crura  cerebri.  Lying  dorsally  to  the  crus  on 
each  side  is  a  broad  band  of  black  pigmented 
cells,  forming  the  substantia  nigra.  The  grey 
matter  around  the  aqueduct  is  considerable,  the 
posterior  longitudinal  bundle  is  somewhat  less  con- 
spicuous than  below  and  forms  a  narrow  band 
lying  at  the  ventral  edge  of  the  central  grey  matter. 
Large  nerve  cells  lie  in  the  ventral  portion  of  this 
grey  matter,  forming  the  nuclei  of  the  third  nerve,  the 
fibres  of  which  can  be  seen  passing  ventrally  in  many 
bundles.  In  the  middle  line  between  these  roots 
a  well-marked  raphe  is  visible.  Lying  midway 
between  the  central  grey  matter  and  the  substantia 


230 


Elements  of  Histology 


nigi'a  is  a  large  mass  of  cells,  known  as  the  red 
nucleus.  In  man  this  nucleus  consists  of  cells  vary- 
ing in  size   from   20-7 5yu.       These  nuclei  have  some 


R.N 


Fi< 


14S.— Section  through  the  Anterioi-  Corpora  Quadrlgemina. 
graj^li  of  a  Weigert-Pal  preparation.) 


{Photo- 


The  section  is  somewhat  oblique,  lieing  slightly  higher  on  the  right  side  than 
the  left.  The  symmetrical  projections  above  are  the  anterior  corpora  quadrl- 
gemina. The  openiii!.'  between  them  is  the  Sylvian  aqueduct.  Tlie  lighter 
substance  around  this  is  the  grey  matter  surrounding  the  iter.  The  darker 
masses  forming  tlie  lower  Ijoundary  of  this  L'rey  matter  arranged  in  discrete 
areas  on  right  side  are  the  posterior  longitudinal  bundles,  lyins  in  which  are 
cells  forming  the  nucleus  of  the  third  nt- rve.  The  bundles  of  fibres  passing 
in  an  arched  manner  downwards  from  the  third  nucleus  are  the  fibres  of  the 
third  nerve.  At  level  r.  x.  on  right  side  is  a  large  dark  mass  lyin.L'  in  a  still 
darker  patch,  having  the  tibres  of  the  third  passing  throusrh  its  median 
region.  This  is  the  commencement  of  the  red  nucleus,  which  is  not  yet 
evident  on  the  left  side,  where  a  corresponding  dark  mass  consists  of  the 
decussated  fibres  of  the  suiierior  cerebellar  peduncle.  On  the  left  side  lying 
below  and  laterally  to  this  mass  and  light  in  shade  is  the  substantia  nigra, 
this  forms  the  base  of  a  projection  (the  cms  cerebrii,  in  which  the  fibres  of 
•  thepyramids  and  other  fibres  pass  longitudinally.  The  dark  band  somewhat 
arched  passing  upwards  to  the  anterior  corpus  quadrigeminum  from  the  dark 
mass  of  the  superior  cerebellar  peduncle  is  the  fillet. 


Medulla    Oblongata.  231 

connection  with  the  superior  cerebellar  peduncles, 
which  terminate  liere  in  their  uj)\vard  course. 
Laterally,  the  tillet  is  seen  passing  dorsally  towards 
the  prominent  <niferior  corpus  quadrigeminum.  A 
small  portion  of  the  brachiuiii  of  the  latter  may  also 
be  seen.  The  ujjward  continuation  of  the  reticular 
formation  corresponds  to  the  mass  between  the  ventral 
aspect  of  the  central  grey  matter  and  the  substantia 
nigra,  and  is  called  the  tegmeiituni.  The  locus 
coeruleus  is  no  longer  seen,  but  the  descending  fifth 
is  still  apparent. 

Structure  of  the  anterior  corpus  quadrigeiidnurn. 
Externally  there  is  a  thin  layer  of  white  matter  about 
30-40)1/  in  thickness.  This  is  known  as  (a)  the 
stratum  zonale.  The  white  fibres  in  this  layer  pass 
through  the  superior  brachium  from  the  optic  tracts. 
From  the  layer  many  fibres  enter  the  inner  layers, 
and  in  them  form  dendritic  ramifications,  {h)  The 
stratum  cinereum.  In  this  layer  are  numerous  cells, 
whose  neuraxons  pass  inwards,  (c)  The  stratum  alho- 
cinereum.  externum.  This  layer  contains  numerous 
small  and  large  cells  and  nerve  fibres.  The  nerve 
fibres  enter  the  layer  largely  from  the  optic  tract  by 
the  superior  brachium.  A  considerable  amount  of  de- 
cussation of  these  fibres  occurs  on  the  median  side  with 
those  of  the  opposite  corpus  quadrigeminum  anterius. 
(d)  The  stratum  cdbo-<-inereuin  internum.  (Stratum 
lemnisci.)  This  layer  is  subdivided  into  three  minor 
layers  :  (a)  the  fillet  layer,  formed  from  a  continua- 
tion of  the  dorsal  part  of  the  median  fillet  and  from  the 
lateral  fillet ;  (/3)  a  layer  of  grey  matter  ;  (y)  a  layer 
of  arched  filjres  bordering  the  central  grey  matter 
and  decussating  in  the  middle  line.  All  these  layers 
are  pervaded  by  radial  fibres  passing  from  the  central 
grey  matter. 

The   optic    lobes    of    birds    have    been  more  fully 
examined    as    regards    the    various    layers  and   their 


232  Elements  of  Histology. 

connections.  Dilierent  authors  divide  these  structures 
in  various  different  layers.  Adopting  Kulliker's 
description,  a  vertical  section  may  be  regarded  as 
showing^(l)  a  superficial  layer  of  fibres  from  the  optic 
tract  ;  (2)  and  (3)  layers  of  grey  matter  or  molecu- 
lar layers  :  in  (2)  the  optic  nerve  fibres  form  their 
dendritic  ramifications  ;  (4)  a  layer  of  white  fibres 
arranged  in  a  kind  of  lattice  work  ;  (5)  an  inner  layer 
of  white  fibres  in  which  course  the  cerebral  visual 
fibres ;  (6)  a  layer  of  grey  matter  lying  against  the 
ependyma  of  the  ventricle  of  the  optic  lobes.  The 
connections  of  the  cells  and  fibres  of  this  layer  have 
been  established  by  Golgi's  method  by  Ramon  y  Cajal 
and  V.  Gehuchten. 

In  the  corjDora  quadrigemina  important  con- 
nections are  made  by  the  fillet  fibres.  Some  of  these 
connections  have  already  been  referred  to  (s$193).  Tlie 
fillet  fibres  in  their  upward  course  give  ofl'  collaterals 
which  ramify  or  actually  terminate  themselves  in  the 
cells  of  the  nucleus  of  the  lateral  fillet.  Many  of  the 
fillet  fibres  terminate  in  dendritic  ramifications  in 
the  cells  of  the  posterior  corpora  quadrigemina,  many 
others  pass  into  the  anterior.  The  cells  of  the  lateral 
nucleus  originate  fibres  which  pass  possibly  towards  the 
cerebrum;  some, however, descend  towards  the  superior 
olive.  Some  of  the  fibres  entering  both  corpora 
quadrigemina  decussate  dorsally  and  pass  to  the 
opposite  corpora.  There  may  also  be  some  connection 
amongst  the  fillet  fibres  with  those  of  the  superior 
cerebellar  peduncle. 

The  nucleus  of  the  third  nerve  has  been  described 
as  consisting  of  many  various  groups  of  cells.  It  is  to 
be  regarded  as  mainly  one  nucleus,  extending  through 
the  whole  length  of  the  anterior  corpus  quadri- 
geminum  and  somewhat  above  it.  It  consists  of  a 
main  mass  with  two  less  distinct  masses  :  a  dorso- 
lateral   with    larsre    cells,   and    a    dorso-median    with 


Med  ul  l  a   Ob  l  onga  ta.  233 

smaller  cells.  At  3ts  cerebral  end  there  is  a  central 
mass  having  large  cells.  It  has  been  suggested  that 
the  dorso-niedian  group  of  small  cells  supplies  the 
internal  muscles  of  the  eye  (sphincter,  ciliary).  The 
nucleus  is  presumably  connected  with  the  pyramidal 
tracts.  Arborescences  around  cells  of  the  third 
nucleus  are  to  be  seen  in  new-born  animals,  and  the 
fibres  forming  them  may  be  followed  to  the  raphe, 
crossing  here  and  coursing  ventrally.  Connections 
also  exist  with  the  posterior  longitudinal  bundle. 
This  bundle  is  to  be  regarded  as  the  upward 
continuation  of  part  of  the  anterior  column  of  the 
cord,  forming  short  longitudinal  commissures  It  is 
associated  with  the  hypoglossal  nucleus,  tho>e  of  the 
vago-accessory,  the  fifth  and  the  acoustic  (vestibular 
branch).  Connections  also  exist  with  the  sixth, 
fourth,  and  third  nuclei.  The  posterior  longitudind 
bundle  furnishes,  therefore,  commissural  connections 
between  the  different  eye  muscles.  Connections 
of  the  third  nucleus  also  exist  with  the  optic 
nerves. 

The  hracJiia  passing  to  the  corpora  quadrigemina 
are  spoken  of  as  the  superior  or  anterior  and  the 
inferior  or  posterior.  The  fibres  of  the  superior  pass 
to  the  lateral  corpus  geniculatum  and  to  the 
occipital  tract.  The  fibres  of  the  inferior  brachium 
are  connected  with  the  median  corpus  geniculatum 
and  possibly  may  pass  through  the  tegmentum  by 
the  internal  capsule  to  the  temporal  region. 

That  portion  of  a  transverse  section  through  the 
region  of  the  corpora  quidrigemina  which  projects 
ventrally  into  the  two  crura  is  sometimes  S[)oken 
of  as  the  crusta,  being  separated  from  the  remainder 
(tegmentum)  of  the  region  ventral  to  the  aqueduct  by 
the  substantia  nigra.  The  crusta  contains,  in  addition 
to  the  fil)res  derived  from  the  pyramids  which  occupy 
a  central  portion  in   each   crus,  other  fibres   derived 


23  4  Elemexts  of  Histology. 

from  the  pons.  Those  on  the  median  side  pass  to 
the  frontal  region,  those  on  the  lateral  portion 
to  the  temporal  and  occipital  regions.  Some  fibres 
on  the  median  side  are  derived  from  the  median 
fillet. 


235 


CHAPTER  XIX. 

THE  CEREBRUM  AND  CEREBELLUM. 

196.  The  structure  of  the  dura  mater,  araclinoidea, 
and  pia  mater  of  the  brain  is  simihir  to  that  of  the 
same  membranes  of  the  cord. 

As  has  been  shown  by  Boehm,  Key  and  lletzius, 
and  others,  the  deeper  part  of  the  dura  contains 
peculiar  ampullated  dilatations  connected  with  the 
capillary  l)lood- vessels,  and  forming  in  fact  the  roots 
of  the  veins. 

The  glanduhe  Pacchioni^  or  arachnoidal  villi  of 
Lnschka,  are  composed  of  a  spongy  connective  tissue, 
prolonged  from  the  sub-arachnoidal  tissue  and  covered 
with  the  arachnoidal  membrane.  These  prolongations 
are  pear-shaped  or  spindle-shajDed,  with  a  thin  stalk. 
They  are  pushed  through  holes  of  the  inner  part  of 
the  dura  mater  into  the  venous  sinuses  of  this  latter, 
but  are  covered  with  endothelium.  Injected  material 
passes  from  the  sub-arachnoidal  sjiaces  through  these 
stalks  into  the  villi.  Tlie  spaces  of  their  spongy 
substance  become  thereby  filled  and  enlarged,  and 
finally  the  injection  matter  enters  the  venous  sinus 
itself.  The  pia  cerebralis  is  very  rich  in  blood-vessels, 
like  that  of  the  cord,  which  pass  to  and  from  the 
brain  substance.  The  capillaries  of  the  pia  mater 
possess  an  outer  endothelial  sheath.  The  plexus 
choroideus  is  covered  with  a  layer  of  polyhedral 
epithelial  cells,  which  are  ciliated  in  the  embryo  and 
in  the  young  subject. 

197.  As  was  mentioned  of  the  cord,  so  also  in  the 


236  Elements  of  Histology. 

brain  the  subdural  lymph  space  does  not  commu- 
nicate with  the  sub-arachnoidal  spaces  or  with  the 
ventricles  (Luschka,  Key  and  Retzius).  Nor  does 
there  exist  a  communication  between  the  sub- 
arachnoidal space  and  a  space  described  by  His  to 
exist  between  pia  mater  and  brain  surface,  but 
doubted  by  others.  The  relations  between  the  cere- 
bral nerves  and  the  membranes  of  the  brain  and 
the  lymph  spaces  of  both,  are  the  same  as  those 
previously  described  in  the  case  of  the  cord  and 
the  spinal  nerves. 

The  pia  mater  ])asses  with  the  larger  blood-vessels 
into  the  brain  substance  by  the  sulci  of  the  cerebrum 
and  cerebellum. 

In  the  white  and  grey  matter  of  the  brain  we  find 
the  same  kind  of  supporting  tissue  that  we  described 
in  the  cord  as  neuroglia.  In  tlie  brain  also  it  is 
composed  of  a  homogeneous  matrix,  of  a  network  of 
neuroglia  fibrils,  and  of  branched,  flattened  neuroglia 
cells,  called  Deit^rss  cells. 

In  the  white  matter  of  the  brain  the  neuroglia 
contains  between  the  bundles  of  the  nerve  fibres 
rows  of  small  nucleated  cells  ;  tliese  form  s})ecial 
accumulations  in  the  bulbi  olfactorii,  and  in  the 
cerebellum.  Lymph  corpuscles  may  be  met  with 
in  the  neuroglia,  especially  around  the  blood-vessels 
and  ganglion  cells. 

All  the  ventricles,  including  the  aqueductus  Sylvii, 
are  lined  witli  a  layer  of  neuroglia,  being  a  direct 
continuation  of  that  lining  the  fourth  ventiicle, 
and  this  again  being  a  direct  continuation  of  the 
central  grey  nucleus  of  the  cord.  Like  the  central 
canal  of  the  cord,  also,  the  ventricles  are  lined 
with  a  layer  of  ciliated  columnar,  or  short  columnar 
epithelial  cells. 

The  blood-vessels  form  a  denser  capillary  net- 
work in  the  grey  than   in   the   white   matter  ;  in   the 


Cerebrum  and  Cerebellum.  237 

latter  the  network  is  pre-eminently  of  a  longitudinal 
arrangement,  i.e.  parallel  to  the  long  axis  of  the 
bundles  of  the  nerve  fibres.  In  the  grey  cortex  of 
the  hemispheres  of  the  cerebrum  and  cerebellum, 
many  of  the  capillary  blood-A'essels  have  an  arrange- 
ment vertical  to  the  surface,  but  are  connected 
with  one  another  by  numerous  transverse  branches. 

The  blood-vessels  of  the  brain  are  situated  in 
spaces,  perivascular  lymph  spaces,  traversed  by  fibres 
passing  between  the  adventitia  of  the  vessels,  and 
the  neuroglia  forming  the  boundary  of  the  space. 
There  are  no  separate  lymphatic  vessels  in  the  grey 
or  white  substance. 

198.  The  white  iiiaftei*  consists  of  medullated 
nerve  fibres,  which  like  those  of  the  cord  possess  no 
neurilemma  or  nuclei  of  nerve  corpuscles,  and  no 
constrictions  of  Ranvier.  The  nerve  fibres  are  of 
very  various  sizes,  according  to  the  locality.  Divisions 
occur  very  often.  When  isolated  the  fibres  show  the 
varicosities  mentioned  in  the  cord. 

The  grey  iiiattei*  consists,  like  that  of  the  cord 
and  medulla,  of  a  basis  of  neuroglia  in  which  are 
embedded  nerve  cells.  The  dendritic  ramifications 
from  the  nerve  cells,  with  medullated  and  non- 
medullated  nerve  fibres,  form  a  large  proportion  also 
of  the  grey  matter. 

With  regard  to  the  structure  of  the  ganglion  cells 
of  the  brain  and  medulla,  what  has  been  mentioned 
of  the  ganijlion  cells  of  the  cord  holds  good  as  to 
them.  Like  the  former,  those  of  the  medulla  and 
brain  are  situated  in  pericellular  lymph  spaces 
(Obersteiner). 

199.  We  now  proceed  to  consider  in  detail  the 
structure  of  the  different  parts  of  the  cerebellum  and 
cerebrum. 

The  cerebelliiiii  is  composed  of  laminated  folds, 
or   convolutions,   and   these    again   are   composed  of 


238 


Elements  of  Histology 


secondary  folds,  each  of  which  consists  of  a  central 
tract  of  white  matter  covered  with  grey  matter.  The 
tracts  of  white  matter  of  neisfhhourinfr  convolutions  of 
one  lobe  or  division  join,  and  thus  form  the  principal 
tracts  of  wdiite  matter. 

The  white  matter  of   the  cerebellar  hemisphere  is 


Fig.  149. — Photograiu  through  the  grey  matter  of  the  cereliellmn  of  tlie 
dog,  showing  the  hiyer  of  Purkinje's  ganglion  cells  with  their  dendrites 
ramifying  in  the  grey  cortex.     {Lov  magnification.) 


connected  (a)  with  the  medulla  oblongata  by  the 
corpus  restiforme,  this  forming  the  inferior  peduncle 
of  the  cerebellum ;  (6)  with  the  cerebrum  by  the 
processus  cerebelli  ad  cerebrum,  this  forming  the 
superior  peduncle  ;  and  (r)  with  the  other  cerebellar 
hemisphere  by  the  tracts  connecting  with   the  pons 


Cerebrum  and   Cerebellum.  239 

varolii ;  these  are  the  pedunculi  cerebelli  ad  pontem, 
or  the  middle  peduncles. 

200.  On  a  vertical  section  through  a  lamina  of  the 
cerebellum  (Fig.  149),  the  following  layers  are  seen:  {a) 
the  pia  mater  covering  the  general  surface,  and  pene- 
trating with  the  larger  blood-vessels  into  the  superficial 
substance  of  the  lamina  ;  (6)  a  thick  layer  of  cortical 
grey  matter ;  (c)  the  layer  of  Purkinje's  ganglion 
cells  ;  {d)  the  nuclear  layer  ;  and  (e)  the  central  white 
matter. 

201.  The  layer  of  ganglion  cells  of  Purkinje  is 
the  most  interesting  layer ;  it  consists  of  a  single  row 
of  large  multipolar  ganglion  cells,  each  with  a  large 
vesicular  nucleus.  Each  possesses  also  a  thin  axis- 
cylinder  process,  directed  towards  the  depth,  the 
cell  sending  out  in  the  opposite  direction — i.e.  towards 
the  surface — a  thick  process  which  soon  branches 
like  the  antlers  of  a  deer,  the  processes  being  all  very 
long-branched  and  pursuing  a  vertical  course  towards 
the  surface  ;  sooner  or  later  they  all  break  up  into 
the  fine  nervous  network  of  the  grey  cortex.  The 
longest  processes  reach  near  to  the  surface.  The 
layer  (6)  above  mentioned — i.e.  the  cortical  grey 
matter — is  in  reality  the  terminal  nerve  network 
for  the  branched  processes  of  the  ganglion  cells  of 
Purkinje.  San  key  maintained,  before  the  adoption  of 
more  modern  methods  of  research,  that  in  the  human 
cerebellum  there  are  also  small  multipolar  ganglion 
cells  connected  with  the  processes  of  Purkinje's  cells. 

202.  The  connections  and  distributions  of  the 
different  cells  of  the  cerebellum  have  been  exhibited 
to  a  considerable  extent  by  the  labours  of  observers 
who  have  followed  the  methods  of  Golgi.  A 
scheme  of  the  main  points  on  these  results  is 
shown  in  Figs.  150  and  151.  Fig.  150  indicates 
the  appearance  represented  in  a  section  across  a 
lamina.    Fig.    151   corresponds  to  a  section  taken  in 


240 


Elements  of  Histology. 


the  direction  of  a  lamina. 
Purkinje  first,  they  are 
extensive  dendritic  ramification,  viewed  transversely, 


Considering  the  cells   of 
seen    to    possess    a   very 


'\^jn\ 


i~Ta 


■ml 


Fig.  150.— Scheme  of  the  Connectiou  of  the  Cells  in  the  Superficial  Grey 
Substance  of  the  Cerebellum.     (After  KoUiker.) 

p,  Xeuraxons  of  Purkinje's  cells  with  collaterals  :  k,  tendril-like  fibres  with  k^ 
their  terminations;  gU  glia  cells;  /,  nio^s  fibres;  m,  small  cells  of  the 
molecular  layer;  vi^,  larare  cells  of  the  same  layer  (basket  cells)  forming 
synapses  round  Purkinje's  cells,  3A-;  gr,  cells  of  the  nuclear  layer  witli 
neuraxons  passing  into  molecular  layers,  here  turning  horizontally  and 
giving  a  punctated  appearance  in  cross-section  ;  n,  the  luxuriant  branching 
of  a  Gblgi's  cell  of  the  second  type. 

passing  through  the  whole  thickness  of  the  molecular 
layer,  as  the  cortical  grey  matter  is  sometimes  called. 
This  ramification  is  less  extensive  viewed  in  the  longi- 
tudinal section  of  a  lamina  (Fig.  150).     The  neuraxon 


Cerebrum  and  Cerebellum. 


241 


passes  throu,<;li  the  uucle;ir  layer  oblkjuely,  giving  off 
collaterals  which  to  some  extent  re-enter  the  molec- 
ular layer,  then  the  axon  passing  fiom  the  nuclear 
layer  enters  the  central  white  matter.  There  are  also 
seen  in  the  molecular  layer  other  fairly  conspicuous 


Fig.  151.— Longitudinal  Section  of  the  Grey  Substance  of  the  Ceiebelliun. 
{After  Kolliker.) 

The  restricted  branching  of  the  cells  of  Purkinje  (v)  is  seen.  Tbe  nuclear 
cells  below  are  seen  sending  axons  upwards  inio  the  luoleciilar  layer  which 
divide  dichotomously,  and  run  longitudinally. 


cells  (m'),  which  are  termed  backet  cells.  These  cells 
have  dendrites  Avhich  ramify  amongst  those  of  the 
Purkinje's  cells,  and  a  neuraxon  which  gives  off 
collaterals,  and  these  again  form  arborescences  around 
the  Purkinje  cells.  Other  smaller  cells  [in)  have 
])rocesses  all  of  which  i-amify  in  the  neighbourhood  of 
the  cell.  On  the  border  line  between  the  nuclear  and 
molecular  layers  may  be  seen  large  multipolar  cells 

Q 


242 


Elements  of  Histology 


(sometimes  spoken  cf  as  Goh/i's*  cells),  which  exhibit 
a  dendritic  ramification  in  the  nuclear  laj^er,  and  in 
which  the  neuraxon,  on  entering  the   molecular  layer, 


Ne  - 


Fig.  152.— From  a  Transverse  Section  through  the  Edge  of  the  Restiform 
Body,  PC,  and  the  Tuberculuia  Acustieum  of  the  new-born  Cat. 
{Gofgi.  Kolliker,  II.) 

Xe,  Xerve  fibres  of  the  coclilear  nerve  :  Ne',  the  same  fibres  passing  round  the 
peduncle  ;  c,  collaterals  :  T,  large  ganglion  cells  of  the  tuberculinu  ;  n,  their 
axons  becoming  fibres  of  the  stria?  acustica'. 


divides  up  not  far  from  the  main  cell.  In  the  nuclear 
layer  are  numerous  small  cells  (fjr),  the  dendrites 
dividing    verv    near    to    the    cells,    the    neuraxons. 


*  Though  referred  to  frequently  as  ^^ cells  of  Golgi,''''  these 
are  more  correctly  described  as  "alls  of  the, second  tt/pe  of  Golgi.'" 
Some  authors  use  the  term  "cells  of  Golgi"  to  refer  to  neu- 
roglia cells. 


Cerebrum  and  Cerebellum.  243 

however,  pass  into  the  iiiolecuhir  hiyer  and  bifurcate 
longitudinally  (Fig.  150)  at  various  levels.  The  so- 
called  "molecular"  condition  of  the  cortical  grey  matter 
is  largely  due  to  the  appearance  of  these  fibres  being 
cut  across  as  well  as  to  the  sections  of  the  processes 
of  the  cells  of  Purkinje.  The  central  white  matter 
shows  other  fibres  than  those  representing  the 
neuraxons  of  the  Purkinje  cells  (Fig.  151).  One  set 
of  these  terminate  in  arborescent  tufts  in  the  nuclear 
layer,  and  are  referred  to  as  moss  fibres  {/).  Another 
set  pass  into  the  molecular  layer  and  break  up  on 
connection  with  the  dendrons  of  the  cells  of  Purkinje. 
These  are  spoken  of  as  tendril  fibres.  These  two 
sets  of  fibres  are  to  be  regarded  as  conducting  to  the 
grey  matter  of  the  cerebellum.  In  addition  to  the 
proper  nerve  cells  already  described,  may  be  seen 
neuroglia  cells  (gl).  These  are  also  present  in  the 
central  white  matter  (Fig.  152). 

20.3.  The  structure  of  the  cerebral  con- 
volutions in  g-eneral. — In  a  vertical  section 
through  a  cerebral  convolution  one  is  able  to  see  with 
the  naked  eye  a  central  core  of  white  matter  sur- 
rounded by  a  cap  of  grey  or  reddish-grey  matter, 
which  again,  on  careful  observation,  can  be  seen  to 
consist  of  several  alternate  strata  of  lighter  or 
darker  substance.  The  exact  appearance  of  these  dif- 
ferent layers  varies  in  different  parts  of  the  cerebral 
hemispheres. 

In  general,  a  vertical  section  of  a  convolution 
shows  three  main  layers  :  (1)  a  superficial  molecular 
layer,  (2)  a  layer  of  pyramidal  cells,  (3)  a  layer  of 
poly mor pilous  cells.  These  layers  are  subdivisible  into 
several  others  in  different  parts  of  the  hemispheres 
(Fig.  153). 

204.  Structure  of  the  cerebral  convolu- 
tions in  the  reg^ion  of  the  Rolandic  fissure. — 
In  this  region  one  can  distinguish  six  layers,  showing 


Fig.  153.— Vertical  Section  through  tlie  Grey  Cerebral  Cortex  in  the 
Parietal  Region.     (KoUikcr,  II.) 

a,  .Superficial  white  layers  :  6,  onter  layer  of  small  pyramidal  cells:  c,  outer 
laver  of  large  pyramidal  cells;  d,  inner  layer  of  small  pyramidal  cells  ;  e, 
inner  layer  of  large  pyramidal  cells ;  /,  polymorphous  cells. 


Sir.  zon. 


c.s.c. 


R.F. 
Fig.  154. — For  description  see  next  page. 


246  Elements  of  Histology. 

different  characters.  Superficially  is  the  stratum 
zonale  or  moJecidar  layer  (a),  then  the  outer  layer  of 
small  2^y'i'<^'i>^^d^^  cells  {b),  then  (c)  the  outer  layer  of 
large  pyramidal  cells,  followed  by  (cZ)  the  inner  layer 
of  small  iiyramidal  cells,  then  (e)  the  inner  layer  of 
large  lyyramklal  cells,  and,  adjacent  to  the  white 
matter  (/"),  the  layer  of  polymorphous  cells.  These 
cells  are,  to  some  extent,  separated  into  vertical 
columns  by  intercolumnar  bundles  of  nerve  fibres. 
There  are  also,  running  horizontally,  following  the 
contour  of  the  gyrus,  other  more  or  less  defined 
bundles  of  fibres.  Some  of  these  run  in  the  super 
ficial  molecular  layer  ;  two  other  bands  are  disposed 
tan^fentially,  in  the  pyramidal  cell  layer,  the  more 
superficial  being  the  band  of  Vicq  d'Azyr  or  Geunari, 
the  deeper  that  of  Baillarger.  In  general,  the 
neuraxons  of  the  cells  descend  towards,  and  finally, 
pass  into  the  white  matter  (Fig.  ISt).  There  are 
some  cells  in  the  cortex  which  do  not  conform  to 
this  rule.  Amongst  the  pyramidal  cells  may  be 
found  cells  known  as  Martinotti's  cells,  from  which 
the  neuraxons  ascend  towards  the  superficial  molec- 
ular layer.  Cells  known  as  Golgi's  cells  are  also 
to  be  found,  with  neuraxons  passing  towards 
the  surface  and  dividing  up  not  far  from  the 
cell.  The  general  relation  of  the  different  cells  and 
fibres  is  sliown  in  the  accompanying  scheme  (Fig.  15-i) 


Description  o/Fig.  154  [-f-  --15). 

Fie.  154.— Scheme  of  the  Connection  of  the  Cells  of  the  Cerebral  Cortex. 
{After  KoUiker.) 

Pj, Pi,  Smaller  aud  larger  pyramidal  cells,  the  neuraxons  passing  downwards 
on  their  way  to  the  inner  capsule  ;  P3,  pyramidal  cells  forming  a  termination 
in  tlie  corpus  striatum  ;  at  level  M  a  cell  of  Martinotti  with  neuraxon  passing 
upwards  and  terminating  in  stratum  zonale  ;  at  level  G  a  Golgi  cell  (2nd  order) 
with  much-branched  neuraxon  immediately  aliove  it  ;  Ac,  association 
cell,  on  inner  side  of  G  is  a  cell  (Cc)  with  neuraxon  passing  into  corpus 
c-allosum  :  C.S.C.,  a  cell  of  corpus  striatum  with  neuraxon  passing  into  cortex  ; 
R.F..  a  fibre  from  the  fillet  passing  up  into  the  cortex,  one  of  Ramon  y 
Cajal's  fibres  ;  Str.  zon.,  stratum  zonale,  or  superficial  white  layer. 


Fig.  155. — Pyramidal  Cell  of  the  Cortex  of  the  Brain,  its  axon  giving  off 
unmerous  collaterals.    {Kollilcr,  II,) 


Fig.  156. -Fascia  Dentata  and  adjoining  part  of  C-nim  Amnionis  of  Human 
Embryo.     (Aft'^r  KoUiker.) 

^^■'.^'ifL^^iK^^S'^^^^^  bundle,  an  accessory  bundle  pasMnsr  out  to  the  rights  • 
^^f.  ■.  ""i-'?  ''■*^"'"  radwtuni  of  fascia  dentata:  «.  cell  with  ascendiiis  axon 
(cell  of  Martinott.) :  Pi/r..  pyramidal  cells;  F,  flml.ria:  K.   nuclear  laNer 


Cerebrum  and  Cerebellum.  249 

from  Kolliker.  The  pyramidal  cells  have  a  conspicuous 
apical  process,  which  passes  vertically,  giving  off 
lateral  processes,  and  forms  a  system  of  dendrites  in 
the  superficial  molecular  layer.  Other  dendritic 
ramifications  occur  closer  to  the  cell  and  the  neuraxon 
passes  towards  the  white  matter,  giving  off  collaterals 
as  it  traverses  the  grey  substance  (Fig.  155).  Some  of 
the  pyramidal  cells  (Cc)  have  neuraxons  which  pass  to 
the  opposite  hemisphere  in  the  corpus  callosum,  and 
not  towards  the  inner  capsule,  through  which  a  large 
number  of  the  neuraxons  course.  Some  pyramidal 
cells  again  probably  have  their  neuraxons  ter- 
minating in  connection  with  cells  of  the  corpus 
striatum  (P'*).  The  connections  of  a  cell  of  Marti- 
notti  are  seen  (M),  and  those  of  a  Golgi  cell  (G). 
Fibres  conducting  towards  the  cortex  are  repre- 
sented by  (1)  Ramon  y  Cajal's  fibi-es  (R.F.),  passing 
from  the  fillet  and  subdividing  in  the  cortex  ; 
(2)  fibres  from  cells  of  the  corpus  striatum  (C.S.C.) 
passing  up  into  the  grey  matter  of  the  cortex  in  a 
similar  manner. 

205.   Structiii-e  of  the  liippocaiiipus  major 
and  the  fascia  deiitata  (Fig.  156). 

The  hippocampus  as  it  projects  into  the  ventricle 
is  invested  beneath  the  ependyma  with  a  layer  of 
wdiite  fibres  called  the  alveus.  Lying  against  the 
alveus  are  pyramidal  cells,  the  neuraxons  of  which 
pass  into  it  ;  the  conspicuous  apical  process  passes 
through  a  large  ):»ortion  of  the  thickness  of  the  hippo- 
campus, giving  it  a  radiate  appearance  (the  stratum 
radiatum),  and  forming  a  dendritic  ramification  above 
this  in  the  stratum  lacunosum.  Tracing  the  sub- 
stance of  the  hippocampus  towards  the  fascia  dentata, 
these  pyramidal  cells  become  less  conspicuous  and  are 
not  to  be  regarded  as  forming  any  definite  layer  in 
this  region.  The  fascia  dentata  has  externally  a 
superficial  layer  or  stratum  zonale  into  which  pass  the 


250 


Elements  of'  Histology. 


dendritic  ramifications  of  a  layer  of  small  cells,  the 
stratum  (jranuJosum.  From  these  small  cells 
neuraxons  pass  to  the  central  substance  of  the  fascia 


olfc. 


Fig.  157. — Diagram  of  the  Probable  Connections  of  Cells  and  Fibres  in  the 
Olfactory  Bulb.     {After  Schafer.) 

olf.c,  Sensory  cells  of  tlie  olfactor.v  epithelium  ;  olf.n.,  deepest  layer  of  the  liulb 
composed  of  the  olfactory  nerve  fibres  which  are  prolonsed  from  the  olfac- 
tory cells ;  f//., olfactory  shjiueruli,  containing  dendrons  of  hoth  the  olfactory 
nerve  fibres  and  the  mitral  cells;  mc,  mitral  cells;  tx.  their  axons ;  J4.fr., 
nerve  fibres  of  tlie  bulb  becoming  continuous  with  the  olfactory  tract. 


dentata,  and  from  this  also  many  so  called  "moss 
fibres "  issue,  passing  to  the  granular  layer  [Mf 
and  31/"). 

206.  Structure  of  tlie  oHaetory  bulb  (Figs. 
157  and  158). — A  vertical  section  through  the  olfac- 
tory bulb  indicates  considerably  more  development 
on  the  side  lying  against  the  cribriform  plate  than 


Cerebrum  and  Cerebellum. 


251 


on  the  dorsal  side.  Passing  from  the  surface  lying 
on  the  ethmoid  bone,  one  can  make  out  the  following 
la3^ers :  (1)  Bundles  of  olfactory  nerve  fibres;  (2)  the 
zone   of   olfactory   glomeruli  ;   (3)   a    layer    pervaded 


Fig.  158.— From  the   Olfactory  Bulb   of  a  Mouse  24  days  old.     {Highly 
magnified.     Golgi.     KoUiker,  II.) 

C,  Collaterals ;  C;^  glomeruli ;  M,  mitral  cells;  J/',  large  brush  cell  ;    .172,  small 
ditto ;  n,  neuraxon. 

by  many  irregular  fibres,  giving  it  the  character  of 
a  molecular  layer,  and  containing  the  so-called  ^nitral 
nerve  cells  ;  (4)  a  nuclear  layer  composed  of  small 
cells  ;  (5)  a  layer  of  longitudinal  nerve  fibres  ;  (6) 
the  neuroglia  forming   the   central  substance.       The 


252  Elements  of  Histology. 

connection  of  these  mitral  cells  is  indicated  in  Figs.  157 
and  158.  One  or  two  processes  pass  horizontally  and 
an  axis-cylinder  process  passes  through  the  nuclear 
layer  towards  the  layer  of  longitudinal  nerve  fibres. 
One  conspicuous  process  passes  towards  the  glomeruli 
and,  entering  one  of  the  masses,  forms  a  dendritic 
clump.  Similarly  axons  from  the  olfactory  cells  in  the 
nose  pass  to  these  glomeruli  and  form  dendritic  clumps. 
These  glomeruli  are  definite  localities  where  connec- 
tions are  established  between  cells  of  the  olfactory 
bulb  and  the  olfactory  mucous  membrane. 


25. 


CHAPTER  XX. 


THE    CEREBRO  SPINAL    GANGLIA. 


207.  The  ganglia  connected  with  the  posterior 
roots  of  the  spinal  nerves,  and  with  some  of  the 
roots  of  the  cere- 
bral nerves  —  Gas- 
serian,  otic,  genic- 
n  1  a  t  e,  ciliary, 
Meckel's  ganglion, 
the  ganglia  of  the 
branches  of  the 
acoustic  nerve,  the 
submaxillary  gan- 
glion, etc. — possess 
a  capsule  of  fibrous 
connective  tissue 
continuous  with  the 
epineurium  of  the 
afferent  and  efferent 
nerve  trunks  (Fig. 
159).  The  interior 
of  the  ganglion  is 
subdivided  into 

smaller  or  larger 
divisions,  contain- 
ing nerve  bundles 
with  their  perineu- 
rium, or  larger  and 
smaller    groups     of 

c'an.a'lion  cells  In  Fig-    1j9— Spinal    Ganglion    of   the   Lumbar 

^,      °       .       ,      '■        ,.  Region  of  a  Puppy.  {KoUiler,  II.) 

the     spinal     ganglia  c,  Ganglion  with  its  cells  and  their  axons;   Bp, 
fVlpop        latter         ^''^^         posterior;  Ita,  anterior  branch  ;  M,  motor  ;  S, 


are 


sensory  root. 


254 


Elements  of  Histology. 


generally  disposed  about  the  cortical  part,  whereas 
the  centre  of  the  ganglia  is  chiefly  occupied  by 
bundles  of  nerve  fibres. 

208.  The  ganglion  cells  differ  very  greatly  in  size — 


YVj..  Ii30.— Transverse  Section  of  the  Spinal  Cord  of  a  Chick  of  the  9th  day 
of  incubation.     {Afttr  Ramon  y  Cajal,  from  Quain's  "  Aimtomy.") 

A,  Axons— anterior  root  fibres— issuing  from  large  ganglion  cells  of  anterior 
horn.  C  :  B,  posterior  root  fibres  passing  from  the  bipolar  ganglion  cells  (/),  O 
of  the  spinal  arangliou  into  the  posterior  white  column  Z>.  where  they  bifur- 
cate to  become  longitudinal ;  e,f,g,  collaterals  from  these  fibres  :  b,  fibres  of 
anterior  white  column  in  cross-section. 


some  being  as  big,  and  bigger,  than  a  large  multipolar 
ganglion  cell  of  the  anterior  horn  of  the  cord,  others  much 
smaller  (Fig.  162).  Each  cell  has  a  large  oval  nucleus, 
including  a  network  with   one  or  two  large  nucleoli. 


Cerebrospinal   Ganglia. 


255 


Its  substance  shows  a  distinct  fibrillation.  Each  cell 
of  the  spinal  ganglia  in  man  and  mammals  is  }inipolar 
(Fig.  1G2),  tiask-  or  pear-shaped,  and  invested  in  a 
hyaline  cajisule,  lined  with  a  more  or  less  continuous 


Fig.  161. — From  a  Longitudinal  Section  tlirougli  the  Gasseiian  Ganglion  of 
the  Calf.     {Koinier,   //.) 

layer  of  nucleated  endothelial  cell  plates.  The  single 
process  of  the  ganglion  cell  is  finely  and  longitudi- 
nally striated,  and  is  an  axis-cylinder  process.  Im- 
mediately after  leaving  the  cell  body  it  is  much 
convoluted  (Retzius) ;  it  is  then  covered  with  a 
medullary  sheath,  and  so  becomes  a  medullated  nerve 
fibre.  The  capsule  of  the  ganglion  cell  is  continued 
on  the  axis  cylinder  process,  and,   farther  on,  on  the 


256 


Elements  of  Histology. 


meclullated    ner\'e    fibre,    as    the    neurilemma ;    the 

endothelial  plates  of  the  capsule  pass  into  the  nerve 


Fig.  1(32.  —  Large  and  Small 
Ganglion  Cell  of  the  Ganglion 
Gasseri  of  RabVdt.  (A'ei/  and 
Retzhts.) 

The  axis  cylinder,  after  leaving  the 
cell,  becomes  convoluted  and 
transformed  into  a  medullated 
nerve  filire.  which  divides  into 
two  medulLited  fibres. 


Fig.  163.— Lsolated  Ganglion  Cell 
of  Spinal  Ganglion  of  Toad. 
{Key  and  Retzius.) 

The  axis  cylinder  process  becomes 
transformed  into  a  medullated 
nerve  fibre.  The  capsule  of  the 
cell  IS  prolonged  as  the  neu- 
rilemma of  the  nerve  fibre. 


corpuscles  linin^  the  neurilemma,  their  number  greatly 
diminishing  (Fig.  162). 

209.  In  the  rabbit  this  medullated  nerve  fibre  at 
its  first  node  of  Ranvier,  which  is  not  at  a  great  dis- 
tance from  the  ganglion  cell,  divides  into  two  medul- 
lated nerve   fibres   in   the  shape  of  T  ;    one    branch 


Cer  ebr  0-spina  l   Ga  ngl  I  a.  257 

passes  to  the  cord  as  a  posterior  root  fibre,  the  other 
to  the  peripher}^  (^ig-  1(^3).  In  man,  this  T-shaped 
division  has  also  been  observed  by  Retzius,  but, 
though  liighly  proljable,  it  cannot  be  said  to  have 
been  actually  pro\ed  that  in  rabbit  or  man  every 
axis-cylinder  process  shows  this  T-shaped  division. 
Retzius  obser\'ed  this  T-shaped  division  also  in  the 
Gasserian,  geniculate,  and  ^■agus  ganglia  in  man. 

The  ganglion  cells  are  not  unipolar  in  all  cerebral 
ganglia  ;  in  the  ciliary  and  optic  ganglia  there  are 
ganglion  cells  which  are  multipolar. 

210.  Numerous  ganglia  of  microscopic  size  are  to 
be  found  in  the  submaxillary  (salivary)  gland  :  they 
are  of  ditferent  sizes,  and  are  in  reality  ganglionic 
enlargements  of  larger  or  smaller  nerve  bundles. 
Each  ganglion  is  invested  in  connective  tissue  con- 
tinuous with  the  perineurium,  and  the  ganglion  cells 
are  unipolar,  and  of  the  same  nature  as  those  described 
above,  each  cell  being  possessed  of  an  axis-cylinder 
process,  which  becomes  soon  a  nerve  fibre.  At  the 
back  of  the  tongue  there  are  similar  small  micro- 
scopic ganglia. 


R 


258 


CHAPTER    XXI. 


THE    SYMPATHETIC    SYSTEM. 


211.  The  sympathetic  nerve  branches  exactly  re- 
semble the  cerebro-spinal  nerves  in  their  connective- 
tissue  investments  (epi-,  ])eri-,  and  endoneurium)^  and 


Fig.  164.— Sympathetic  Nerves.     (Atlas.) 


A,  Small  Imndle  invested  in  an  endothelial  sheatli,  iierineurium  ;  b,  one 
raediillated  and  three  non-medullated  nerve  flbres  of  various  sizes;  the 
largest  shows  division  ;  c,  two  varicose  nerve  flbres. 

in  the  arrangement  of  the  fibres  in  bundles  (Fig.  164,  a). 
Most  of  the  nerve  fibres  in  the  bundles  are  non- 
medullated  or  Remak's  fibres  (Fig.  164a),  each  being 
an   axis    cylinder   invested    in    a    neurilemma,    with 


5 J  -MP A  TH E  TIC    SyS  TEM. 


259 


oblong  nuclei  indicative  of  nerve  corpuscles  (Fig. 
1G4,  b).  But  there  are  some  meJullated  nerve  fibres 
to  be  met  with  in  each  bundle,  at  least,  of  the 
hirger  nei"ve  trunks.  These  in  some  cases  show 
the  medullary  sheath  more  or  less  discontinuous, 
and    "with  a  vari- 


cose  outline  (Fig. 
lG-1,  c),  owing  to 
a  uniform  local 
accumulation  of 
fluid  between  it 
and  the  axis  cyl- 
inder. The  small 
or  microscopic 
bundles  of  nerve 
fibres  possess  an 
endothelial  (peri- 
neural) sheath. 
The  small  and 
large  branches 
always  form 
plexuses. 

212.  The  gan- 
glia of  the  sym- 
pathetic chain 
(Fig.  16  5)— lateral 
gancjlia,  as  also 
the  further  sym- 
pathetic ganglia 
— the  collateral 
ganglia    like    the 


'  -  t-'^^  ;^;"'  ^^;>  /r.%    ■ 


Fig.  164a.— Cross-Section  through  part  of  Branch 
of  the  Splenic  Nerse  of  the  Ox,  showing 
bundles  of  non-medullated  or  Remak's  fibres 
in  cross-section  ;  the  nerve  fibres  being  com- 
posed of  fibrillK  appear  granular  in  cross- 
section  ;  the  nuclei  here  shown  belong  to  the 
neurilemma  of  the  fibres.    {Kolliker,  II.) 


semilunar  and  the 

cardiac  ganglia,  and  the  peripheral  ganglia,  like  those 
on  and  in  the  abdominal  viscera,  are  microscopic 
in  size,  but  possess  in  a  general  way  the  same  structure 
as  the  cerebro-spinal  ganglia.  The  ganglion  cells  are 
bipolar,  or  more  commonly  multipolar.      Such  are  the 


26o 


Elements  of  flisroLOGV. 


microscopic  ganglionic  enlargements  on  many  of  the 
sympathetic  nerve  l)ranclies  in  the  thoracic  and 
abdominal  organs. 

Thev  occur  in  some  organs  very  numerously — e.g. 
,■7,,^,,^  alimentary      canal, 

urinary  bladder  (Fig. 
166  and  Fig.  167), 
respiratory  organs, 
salivary  glands — and 
are  of  all  sizes,  from 
a  few  ganglion  cells 
placed  between,  or 
laterally  to,  the  nerve 
tibres  of  a  small  bundle, 
to  oval,  spherical,  or 
irregularly  -  shayyed 
masses  of  ganglion 
cells  placed  in  the 
course  of  a  large  nerve 
bundle,  or  situated  at 
the  point  of  anasto- 
mosis of  two  or  more 
nerve  branches  ( Fig. 
167). 

213.  The  fjanglia 
in  connection  with  the 
plexuses  of  nerve 
branches  of  the  heart, 
the  cjanwlia  in  the 
plexus  of  non-medul- 
lated  nerve  tibres  ex- 
isting between  the 
longitudinal  and  cir- 
cular  coat  of  the  exter- 
nal muscular  coat  in 
the  aliuientary  canal,  known  as  the  plexus  myen- 
tericus    of   Auerbach,   the   ganglia    in   the   plexus   of 


fig.  165.— Sixth  Ganglion  Thoracicuni  of 
the  Left  Sympathetic  of  the  Rabbit. 
(KoUiker,  //.) 

Re,  Rami  communicantes ;  S,  lirauch  of 
sranslion  containing  two  coarser  and 
several  finer  fibres:  Spl,  srlanchnicus ; 
T,  sympathetic  trunk;  3, ganglion  cells. 


Si  -MPA  THE  TIC    SVS  TEM. 


26t 


nerve  Blanches  of  tlie  submucous  tissue  in  the 
aliiuent;iry  canal,  known  as  Meissner's  plexus  (Fig. 
172),    the    ganglia    in   the   nervous    plexuses    in    the 


Fig.  166.— Group  of   Ganglion  Cells  interposed  in    a    Bundle  of  Sympa- 
thetic Xerve  Fibres  ;  from  the  Bladder  of  Rabbit.     (Handbook.) 

outer  wall  of  the  Vjladcler,  in  the  bronchial  wall,  and 
in  the  trachea,   and  lastly  the  ganglia  in  connection 


Fig.  1G7. — Small  Collection  of  Ganglion  Cells  along   a   small  Bundle   of 
Sympathetic  Nerve  Fibres  in  the  Bladder  of  Rabbit.    {Atlas.) 

Each  gangliou  cell  possesses  a  capsule.    Tlie  substance  of  the  ganglion  cell  is 
prolonged  as  the  axis  cylinder  of  a  nerve  flljre. 

with  the  nerves  supplying  the  ciliary  muscle  of  the 
eye,  all  belong  to  the  sympathetic  .system. 


262 


Elements  of  Histology 


The  ganglion  cells  (Fig.  170)  are  of  very  different 
sizes,  each  possessing  a  large  oval  or  spherical  nucleus 
with  one  or  two  nucleoli.  Their  sliape  is  spherical  or 
ova],  flask -shaped,  club-shaped,  or  pear-shaped  ;  they 


Fig.  168.— Microscopic  Ganglion  in  the  Submaxillary  GlaudofDog.  i^AtUs.') 

c.  Connective  tissue  surrounding  tlie  ganglion  :  g,  tlie  ganglion  cells  with  their 
capsule ;  n,  nerve  fibres. 

possess  either  one,  two,  or  more  processes,  being  uni-, 
bi-,  or  multipolar.  The  cell  is  invested  in  a  capsule 
lined  with  nucleated  cells,  both  being  continued  on 
the  processes  as  neurilemma  and  nerve  corpuscles 
respectively. 

214.   By   the    aid  of  Golgi"s  method  it  has  been 
definitely  established  (Golgi,  Ramon  y  Cajal,  Retzius) 


Sympathetic  System.  263 

that,  like  the  ganglion  cells  in  the  cord,  the  cells  in 
the  ganglia  of  the  sympathetic  system  possess  one 
axis  -  cylinder  process,  axon  or  nenraxon,  which 
remains  unramified  (R^Diun  y  Cajal,  Van  Gehuchten, 


Fig.  100.— Plexus  of  Auerbacli  iu  Rectum  of  Toad.     {Atlas.) 
n.  Xerve  branches  ;  g,  ganglion  cell. 

L.  Sala.  Von  Lenhossek,  Kolliker),  though  sometimes 
it  is  possessed  of  nodose  swellings  (Fig.  171).  It 
passes  into  the  periphery  as  a  non-medullated 
fibre  (as,  for  instance,  the  non-medullated  fibres 
passing  from  the  lateral  ganglia  of  the  sym- 
pathetic back  to  the  spinal  nerves  as  the  grey 
ramus  communicans)  ;  or  as  a  medullated  fibre 
(as  for  instance,  the  medullated  fibres  passing  from 
the    ciliary   ganglion    into    the    ciliary  nerves).     The 


264 


Elements  of  Histology. 


2)ost-ganglionic  fibres  of  Langley  are  fibres  which 
originate  as  the  neuraxon  of  a  sympathetic  gan- 
glion cell  (in  the  lateral,  collateral  or  peripheral 
ganglia,   as   the  case  may   be),   and  hence  pass    into 

muscle  (wall  of 
intestine,  blood- 
vessels, the  viscera). 
The  ganglion  cells 
in  the  microscopic 
peripheral  ganglia 
are  also  multipolar, 
although  there  oc- 
cur amongst  them 
bi-  and  unipolar 
cells  (Ramon  y 
Cajal,  Dogiel,  Kol- 
liker). 

Besides  the 
neuraxou  or  axon 
the  sympathetic 
ganglion  cells  pos- 
sess ramifying  pro- 
cesses - —  dendrites, 
which  resolve  them- 
selves like  those  of 
the  cells  of  the  grey 
matter  of  the  cen- 
tral nervous  system 
into  fine  fibres, 
some  of  them  form- 
ing more  or  less 
distinct  arborisa- 
tions or  dendrons 
(Fig.  171).  An 
interesting  relation  exists  between  the  medullated 
nerve  fibres  which  pass  into  a  sympathetic  gan- 
glion from  a  spinal  nerve  [motor  fibres  passing  from 


Fig.  170.— Synipatlietic  Gauglion  Cell  of  Man. 
(Key  and  Itetzius.) 

The  arnnarlion  cell  ii^  iiniltiiiolar :  each  proce.-s  re- 
ceiving a  iieiirileiunia  from  the  eapsiile  of  the 
cell  beeouies  a  iion-inediiUated  aerve  fibre. 


Sv^'ifPA  THE  TIC    SyS  TEM. 


265 


anterior  roots,  as  also  sensory  fibres  from  the  j)osterior 
roots  and  spinal  ganglia],  as,  for  instance,  those 
passing  from  the  motor  roots  by  the  white  rami  com- 
miinicantes  into  the 
lateral  and  farther 
into  the  collateral 
ganglia,  i.e.  the 
free  -  i/anc/  lionic 
fibres  of  Langley  ; 
these  fibres  ter- 
m  i  n  a  t  e  (Van 
Gehuchten,  L, 

Sal  a,  Dogiel,  Von 
Lenhossek)  as  fine 
ramifications  be- 
tween and  around 
the  ganglion  cells,  or 
they  form  curious, 
more  or  less  dense, 
convolutions  and 
plexus  surrounding 
the  body  of  the 
ganglion  cell  — 
circ  II  m  c  ellul  a  r 
plexus^  as  is  shown 
in  Fig.  173  (Kol- 
liker). 

215.  By  the 
observations  of 
Beale,  Arnold,  Axel, 
Key  and  Retzius,  it 
was  known  that  in 

the  ganglion  cells  of  the  sympathetic  nerves  of  the 
frog,  the  ganglion  cell  substance  passes  on  as  a  straight 
neuraxon  wdiich  continues  its  course  peripherally  as  a 
non-medullated  nerve  fibre  surrounded  by  a  nucleated 
sheath  or  neurilemma — continued  from  the  capsule  of 


Fig.  171. — Three  Multipolar  Ganglion  Cells 
with  their  Axon,  n.  From  the  Ganglion 
Semilunare  of  Dog  one  day  old.  {Kolliker, 
II.) 


266 


Elements  of  Histology. 


the  ganglion  cell.  This  straight  process  is  entwined  by 
a  thin  spiral  fibre  which,  farther  away  from  the  body  of 
the  irancvlion  cell,  is  a  medullated  fibre  ;  it  ramifies 
on    the  substance  of    the    ganglion    cell    (Fig.    174). 


Fig.  172. — Group  of  Ganglion  Cells  from  the  Plexus  of  Meissner  of  a  Puppy  ; 
amongst  them  a  Multipolar  and  several  Unipolar  Cells.    (Kolliker,  II.) 


Arnold,  then  Ehrlich  and  further  Retzius  (the  last 
two  by  ibjection  of  methylene  blue  into  the  blood- 
vessels of  the  living  frog)  have  shown  this  spiral  fibre 
(stained  blue)  to  terminate  on  and  around  the  sub- 
stance of  the  ganglion  cell  as  an  arborisation ;  a 
condition  which  occurs  in  many  parts  of  the  central 
nervous  system  (anterior  grey  cornu,  cerebellum, 
sympathetic    ganglion    cells,     previously    mentioned, 


SVMPATHETIC    SvSTEM. 


267 


etc.),  that  is  to  say,  the  l)odj  of  a  ganglion  cell 
becomes  surrounded  and  ensheathed  as  it  were  by  a 
dendron  of  an  afferent  nerve  fibre,  the  dillerence  being 


Fig.  173.— Circunicellular  Plexus 
from  tlie  Gauglioii  Cervieale 
Supremuin  of  Calf.  (KoUiker, 
II.) 


Fig.  174. — Sympathetic  Ganglion 
Cell  of  Frog,  showing  the 
straight  process  and  the  spiral 
fibre  ;  the  latter  becomes  a 
metlullated  fibre,  {Key  and 
Eetzius.) 


tliat  in  the  sympathetic  cells  of  the  frog  this  afferent 
(inedullated)  fibre  entwines  as  the  spiral  fibre  the 
efterent  axon  (non-mednllated)  of  the  ganglion  cell. 


26S 


CHAPTER     XXri. 

GEXERAL  COXSIDERATIOXS  AS  TO  THE  ANATOMICAL 
COXSTITUTIOX  AND  NATURE  OF  THE  NERVOUS 
SYSTEM. 

216.  We  are  now  in  a  position  to  summarise  the 
general  structure  and  relation  of  the  constituent 
parts  of  the  nervous  system. 

The  nervous  system  consists  of  nerve  cells  or 
ganglion  cells  and  of  nerve  fibres — the  cells  forming 
the  centres,  the  fibres  the  conducting  paths.  The 
ganglion  cells  form  an  integral  part  of  the  central 
nervous  system — brain,  medulla,  and  cord — as  also  of 
the  ganglia  of  the  sympathetic  and  of  the  peripheral 
collections  and  special  nerve  end-corpuscles  in  the 
various  viscera  and  in  the  sense  organs.  The  ner%e 
fibres,  on  the  other  hand,  are  all,  as  far  as  at  present 
known,  axons  or  neuraxons — that  is  to  say,  pro- 
longations of  the  substance  of  the  ganglion  cells  :  by 
these  axons  near  and  distant  centres,  or  ganglion 
cells,  are  brought  in  relation  to  one  another,  as  also 
by  the  peripheral  terminations  of  the  axons  with 
muscles,  skin,  mucous  membranes,  glands,  etc.  The 
whole  nervous  svstem  mav  be  considered  as  consistincr 
of  a  collection  of  units  (Ramun  y  Cajal),  each  such  unit 
being  called  a  neuron  (Waldeyer).  A  neuron,  then, 
is  a  ganglion  cell  with  all  its  processes,  axon  or  axons, 
and  dendrites — be  they  short  or  long — as  well  as  all 
the  ramifications  and  terminations  of  such  axons  and 
dendrites.       While    of    many    parts    of    the    nervous 


SPINAL  OAN&LION  CELL 


MUITI POLAR  CELL 
OF  ANT. HORN 


1        SMN 


Fie.  175.— Sr-heme  of  Relationship  of  Cells  and  Fibres  of  Brain  and  Cord, 
°      prepared  by  Halliburton  and  Mott.     (From  Kirke's  "  Physiology.") 

AB,  Middle  line  tlirough  brain  medulla  and  cord;  pyr.  ijyraniidal  ganglion  cell 
of  the  cerebral  cortex  in  the  Uolandic  area  ;  ax,  axon  of  this  same  gangl  on 
cell,  a  collateral  of  this  axon  passes  in  the  cr)rpus  callosum  (c.  call.)  to 
terminate  in  the  cortex  of  the  other  cerebral  hemisphere  ;  c.stk.,  is  the  corpus 
striatum  :  K.a.c,  s-'anulion  cell  in  the  cerebral  cortex  (nerve  unit  of  associa- 
tion of  Cajali,  around  which  arborises  an  axon  coming  from  a  ganglion  cell 
of  the  optic  thalamus  ;  o.th.,  thalamus  opticus  ;  f,  mesial  hllet ;  s.g.,  nucleus 
gracilis  of  the  meduUa  ;  i.  a.,  axon  ..f  a  ganglion  cell  in  the  nucleus  f-'rac  Us. 
passing  to  the  other  side  as  an  internal  arcuate  hbre;  v,  ganglion  cell  ot 
Purkinje  in  the  corte.x  of  cerebellum  ;  p.ax.,  its  axon  ;  g.m.,  succession  ot 
cell  stations  (units)  in  the  erey  matter  of  the  cord  to  the  optic  thalanu. 


qc.fi,lc.  Leu. 


clcuo  ocuIoTaoLorU'.S 


1        T  Cbrtci  CCrcV: 


Ficr  176.— Diagram  of  the  probable  Connections  and  Relations  of  the  Optic 
Xerve  Fibres  between  the  Ganglion  Cells  of  the  Retina  and  the  Cortex 
Cerebri.     {After  Schdfcr.) 

Between  the  ganffliou  cells  of  the  retina  and  the  lateral  corpus  geniculatum 
or  anterior  corpus  quadrit:eminura  respectively  is  the  rirst  neuron  ;  between 
the  corpus  nuadritrennnum  anterius  and  the  nucleus  oculomotorms  is  a 
second  neuron,  so  also  between  the  lateral  corpus  ireniculatum  and  the  cortex 
cerebri ;  between  the  nucleus  oculomotorius  and  the  cortex  cerebri  on  the 
one  hand  and  the  axons  of  the  tranarlion  cells  of  the  nucleus  oculomotorms 
by  the  nerve  tibres  constituting  the  ocuhiraotor  nerve  terminating  in  the 
muscles  supplied  by  this  on  the  other  hand  is  a  third  neuron. 


Of  the  Nervous  System.  271 

system  the  constituent  units  or  neuronic  are  under- 
stood and  traced  out,  tliere  are  other  parts  in  which 
the  constituent  neurons  have  not  been  as  yet  fully 
worked  out.  Of  the  former  it  has  been  established 
by  the  new  methods  that  the  older  theory  as  to 
anatomical  continuity  between  different  parts  of  the 
nervous  system — i.e.  the  units  or  neurons — is  not 
correct ;  but,  on  the  contrary,  that  the  processes 
(axons  as  well  as  dendrites)  of  one  ganglion  cell  form 
only  contact  with  those  of  others,  as  also  with  peri- 
pheral organs,  ivifhout  direct  contimdty  (Fig.  175). 
Thus,  for  instance,  it  has  been  shown  that  there 
exists  no  direct  or  uninterrupted  continuity  between 
a  motor  (pyramidal)  ganglion  cell,  say  of  the  limb 
centres  in  the  grey  cortex  of  the  brain,  and  the  nerve 
fibres  which  terminate  as  motor  end-plates  or 
dendrons  in  the  muscles  of  the  limbs,  but  that  the 
whole  of  this  path  is  made  up  of  a  succession  or  chain 
of  neurons  or  units ;  and  similarly  beginning  with  a 
dendritic  nerve  termination  in  the  epithelium  of  the 
skin  of  the  limbs  up  to  the  arborising  termination  of 
nerve  fibres  in  the  sensory  centres  of  the  grey  cortex 
of  the  brain,  we  have  no  anatomical  continuity,  but  a 
succession  or  chain  of  units  or  neurons. 

In  each  case,  a  ganglion  cell  with  its  axon,  in- 
clusive of  its  collaterals,  and  its  dendrites,  is  possessed 
of  arborisations  or  dendrons  which  do  not  form  con- 
tinuity with,  but  are  only  in  close  contiguity  to,  the 
arborising  axons,  or  dendrites  respectively*  of  another 
unit  or  neuron  (synapsis).  A  further  point  that 
has  been  established  is  this,  namely,  all  nerve  fibres, 
be  they  medullated  or  non-medullated,  afferent  or 
efferent  fibres,  be  they  of  a  relatively  short  course 
— e.g.  those  beginning  and  ending  within  the  central 
nervous  system — or  do  they  extend  over  long  dis- 
tances like  those  passing  out  from,  or  passing  into, 
the   cord,   medulla,    and  brain   as  spinal  and  crainial 


272  Elements  of  Histology. 

nerves  respectively,  are,  in  reality,  axons  or  direct 
prolongations  of  the  substance  of  ganglion  cells, 
which,  after  a  longer  or  shorter  course,  terminate 
as  arl>orisations  or  dendrons  in  the  periphery  or  in 
the  central  nervous  system,  as  the  case  may  be. 

217.  We  will  illustrate,  by  selecting  a  few  from 
the  many  known  examj)les,  the  nature  and  extent 
of   such  neurons  : — 

(1)  A  motor  neuron  of  the  grey  cortex  cerebri  con- 
sists of  the  following  parts  (Fig.  175)  :  («)  the  cell  body 
of  a  pyramidal  ganglion  cell ;  (6)  its  dendrites,  with 
their  arborisations  in  the  grey  cortex ;  {c)  the  axon 
given  off  as  the  median  basilar  process  and  its  col- 
laterals becoming  medullated  nerve  fibres  of  the  white 
substance  of  the  cortex,  passing  further  through  the 
internal  capsule,  the  pons,  the  anterior  pyramidal 
tract  of  the  medulhi,  the  direct  or  crossed  pyramidal 
tract  of  the  cord,  and  forming  the  tinal  arborisations 
or  dendrons  of  them  and  their  collaterals  in  the 
anterior  cornu  around  the  body  and  dendrites  of  the 
ganglion  cells  in  the  grey  matter  of  the  cord. 

(2)  A  motor  neuron  of  the  grey  anterior  cornu 
of  the  cord  consists  of  :  («)  a  ganglion  cell  in  the 
anterior  grey  cornu  of  the  cord  ;  (6)  its  dendrites 
terminatinix  in  f^itu  as  arborisations  or  dendrons; 
(«:)  the  axon  passing  out  as  a  medullated  nerve  fibre 
through  the  anterior  root,  and  further  through  a 
spinal  nerve,  and  terminating  finally  in  the  periphery 
in  a  striped  muscle  fibre  as  a  dendron — i.e.  the  nerve 
end-plate. 

(3)  A  sensory  neuron  :  (a)  a  ganglion  cell  of  the 
spinal  ganglia  ;  {h)  the  afferent  nerve  fibre — i.e.  the 
distal  portion  of  the  T-shaped  division  of  the  axon, 
coming  from  the  periphery — e.g.  the  skin — by  way  of 
a  medullated  nerve  fibre  of  a  spinal  nerve  ;  in  the  skin 
it  terminates  or  originates  either  in  or  around  special 
nerve  end-corpuscles  or  as  ramifying  fibrillae  in  the 


Of  the  A^F.Ri'ous  System. 


273 


epithelium    of    tlie    smface  ;  (c)  the    efferent    fibre — 
i.e.   the  proximal   branch  of  the   axon  of   the   spinal 


•/•if"'^^^Nkf^)i  /V---"-' 


Fig.  177.— Diagrniu  showing  the  Mode  of  Termination  of  Sensory  Nerve 
Fibres  in  1,  the  auditory,  2,  the  gustatory,  and  3,  the  tactile  sense 
organs  of  vertebrata.  Each  of  these  represents  one  sensory  neuron. 
(After  Retzius,frorii  Qnuin.) 


ganglion   cell   passes  into   the   cord   as   a  medullatecl 
fibre  by  way  of  a  posterior  root  and  farther  into  the 


274 


Elemexts  of  Histology 


posterior  white  colunni  ;    it  or  its  collaterals  finally 
enter  into  the  grey  matter  of  the  cord  or  pass  on  into 

the  nucleus  gracilis  of  the 
bulb,  terminating  as  dendrons 
around  or  close  to  a  ganglion 
cell  (body  or  dendrites)  in 
such  grey  matter  (Fig.  175). 

(4)  A  neuron  of  a  special 
sense  (Figs.  177,  178):  (a) 
the  fjcinolion  cell  in  the  san- 
glion  cell  laj^er  of  the  retina ; 
(J))  its  dendrites  terminating 
as  arborisations  or  dendrons 
in  the  inner  molecular  layer ; 
(c)  the  axon  passing  out  in 
the  opposite  direction  and 
forming  a  fibre  of  the  nerve 
fibre  layer  and  further  pass- 
ing into  the  optic  disc  and 
optic  nerve  as  a  niedullated 
fibre,  pursuing  its  course  as 
such  through  the  chiasma  and 
optic  tract,  and  terminating, 
finally,  in  an  arborisation 
around  cells  in  the  corpus 
geniculatum  or  the  anterior 
corpus  quadrigeminum  (Fig. 
176). 


Fig.  ITS. — Diagram  of  the  Ar- 
rangement of  the  Sensory 
Xerve  Fibres  in  the  Olfactory 
Organ  and  Bixlb.  {After 
Eetzius,  from  Quain.) 

n,  Neuraxon  :  (il.  glomerulus  in 
the  olfactory  bulb.  This  repie- 
seuts  two  consecutive  neurous. 


275 


CHAPTER  XXIII. 


THE    TEETH. 


218.  A    HUMAN    tootll, 

sists  (Fig.  17!))  of  (a)  the 

(b)  the  denfine  forming 
tiie  bulk  of  the  whole 
tooth,  and  surrounding 
the  pulp  cavity  both  of 
the  crown     and     fangs, 

(c)  the  pulp  cavity,  and 
{d)  the  ceinent,  or  crusta 
petrosa.  The  cement 
covers  the  outside  of  the 
dentine  of  the  fang  or 
fangs,  the  enamel  covers 
the  dentine  of  the  crown. 
The  cement  is  covered 
on  its  outside  by  dense 
fibrous  tissue  acting  as 
a  27eriosteuni  to  it,  and 
is  fixed  by  it  to  the 
inner  surface  of  the 
bone  forming  the  wall 
of  the  alveolar  cavity. 

219.  The  enamel 
(Fig.  180)  consists  of 
thin  microscopic  pris- 
matic elements,  the 
enamel  prisms  placed 
closely,  and  extending 
in  a    vertical    direction 


adult  and  milk-tooth,  con- 
enamel  covering  the  crown, 


Fiji  17*> — Loii„Mtu(linal  Section 
till  oUj^h  the  Piceniolai  Tooth  of  Cat. 
{Waldeyer,  in  Strieker's  Manual.) 

a,  Enamel ;  6,  dentine  ;  c,  crusta  petrosa; 
c/ande,  periosteum  ;/,  bone  of  alveolus. 


276 


Elements  of  Histology. 


from  the  surface  to  the  dentine.  When  view^ed  in 
transverse  section,  the  enamel  prisms  appear  of  a 
hexagonal  outline,  and  are  separated  by  a  very  fine 
interstitial  cement  substance.  The  outline  of  the 
enamel  prisms  is  not  straight,  but  wavy,  so  that  the 
prisms  appear  varicose.       The  prisms   are  aggregated 


Fig.  ISO.— Enamel  Prisms.     (Kdllikc,:) 
A,  In  longitiuliual  view  ;  B.in  eross-section. 


into  bundles,  which  are  not  quite  parallel,  but  more 
or  Jess  slightly  overlap  one  another.  On  a  longitudinal 
section  through  a  tooth,  the  appearance  of  alternate 
light  and  dark  stripes  in  the  enamel  is  thus  produced. 
Besides  this  there  are  seen  in  the  enamel  dark  hori- 
zontal curved  lines,  the  brown  parallel  stripes  of 
Retzius,  probably  due  to  inequalities  in  the  density  of 
the  enamel  prisms  produced  by  the  successive  forma- 
tion of  layers  of  the  enamel.  The  enamel  consists 
of  lime  salts — phosphate,  carbonate,  and  fluoride  of 
calcium — with  corresponding  magnesium  salts. 

In  young  teeth  the  free  surface  of  the  enamel 
is  covered  with  a  delicate  cuticle  (the  cuticle  of 
Nasmyth),  a  single  layer  of  non-nucleated  scales. 
In  adult  teeth  this  cuticle  is  wanting,  having  been 
rubbed  off. 


Teeth. 


^11 


220.  The  €l«'iitiii«»  is  tlic  principal  part  of  the  hard 
substances  of  the  tooth,  it  forms  a  coniph^te  invest- 
ment of  tlie  pnl[)  cavity 
of  the  crown  and  fang, 
being  sUghtly  thicker  in 
the  former  than  in  the 
latter  region.  The  den- 
tine is  composed  of  (Fig. 
181):  (l)a  homogeneous 
matrix  ;  this  is  a  re- 
ticular tissue  of  fine 
tibrils  impregnated  with 
lime  salts,  and  thus  re- 
sembling the  matrix  of 
bone ;  (2)  long  fine 
canals,  the  dentinal 
canals  or  tithes,  passing 
in  a  more  or  less  spiral 
manner,  and  vertically 
from  the  inner  to  the 
outer  surface  of  the 
dentine.  These  tubes 
are  branched ;  they 
open  in  the  pulp  cavity 
with  their  broadest  part, 
and  become  smaller  as 
they  approach  the  outer 
surface  of  the  dentine. 
Each  canal  is  lined  with 

a     delicate     sheath — the    Fig.  ISl.— From  a  Section  through  a 
7       ,•       7     7       ,7         T      •!  Canine  Tooth  of  Man.     (Waldeyer,  in 

dentinal,  sheath.  ^    Inside      Strieker's  Mamud.) 

the    tube    is    a    fibre,  the    ((.Crustapetrosa,  with  large  bone  corpus- 
7      ,•        7       /•/  T  1  ties;    b,    interglobular  substance:    c, 

dentinal     JlOre,     a     solid         dentinal  tubules. 

elastic  fibre  originatinsf 

with  its  thickest  part  at  the  pulp  side  of  the  dentine 
from  cells  lining  the  outer  surface  of  the  pulp,  and 
called  odontoblasts. 


278 


Elements  of  Histology. 


On  the  outer  surface  of  tlie  dentine,  both  in  the 
region  of  the  enamel  and  crusta  petrosa,  the  dentinal 
tubes  pass  into  a  layer  of  intercommunicating  irregular 
branched  spaces,  tlie  interglohular  spaces  of  Czermak, 


Fi"^.  18'2.— From  Section  through  the  Pulp  and  Dentine  of  Tooth  of  Guinea- 
pig.     {Photograph,  highly  magnified.) 

Pulp  tissue  with  vessels  in  cross-section;  o,  odontoblasts;  d,  dentine  acci- 
'  dentally  detached  from  odontoblasts. 

or  the  granular  layer  of  Purkinje.  These  communi- 
cate with  spaces  existing  between  the  bundles  of 
enamel  prisms  of  the  crown,  as  well  as  with  the  bone 
lamina  of  the  crusta  petrosa  of  the  fang.  The  inter- 
o-lobular  s})aces  contain  each  a  branched  nucleated  cell. 
The  dentinal  fibres  anastomose  with  the  processes  of 
these  cells.  The  inrrempntal  lines  of  Salter  are  lines 
more  or  less  parallel  to  the  surface,  and  are  due  to 


Teeth. 


279 


imperfectly  calcilied  dentine— the  inter (jlohuhir  anb- 
stance  of  Czerniak.  The  lines  of  Schreger  are  curved 
lines  parallel  to  the  surface,  and  are  due  to  the  optical 
eflect  of  simultaneous  curvatures  of  dentinal  fibres. 


Fig.  183.— Early  Development  of  Tooth.      (Photograph  Inj  ^[,•.  A.  Pringle.) 

l.Tonfrue  in  cross-section  ;  2,  bone  of  jaws;  3,  rudiment  of  enamel  organ  and 
tooth  papilla,  the  former  still  connected  with  the  surface  epithelium. 


221.  The  eeiiieiit  is  osseous  substance,  being 
lamellated  bone  matrix  with  bone  corpuscles.  There 
are  no  Haversian  canals. 

222.  The  pulp  is  richly  supplied  with  blood- 
vessels, forming  networks,  and  extending  chiefly  in 
a  direction  parallel  to  the  long  axis  of  the  tooth. 
Xumerous  medullated  nerve  fibres  forming  plexuses 
are  met  with  in  the  pulp  tissue ;  on  the  outer  surface 


2 So  Elements  of  Histology. 

of  the  pulp  they  become  non-mediillated  fibres,  and 
probably  ascend  in  the  dentinal  tubes.  The  matrix  of 
the  pulp  is  formed  by  a  transparent  network  of  richly 
branched  cells,  similar  to  the  network  of  cells  forming 
the  matrix  of  gelatinous  connective  tissue. 

223.  On  the  outer  surface  of  the  pulp — i.e.  the 
one  in  contact  ^vith  the  inner  surface  of  the  dentine — 
is  a  layer  of  nucleated  cells,  which  are  elongated,  more 
or  less  columnar.  These  are  the  odontoblasts  proper 
(Fig.  182).  Between  them  are  wedged  in  more  or  less 
spindle-shaped  nucleated  cells,  the  outer  or  distal  pro- 
cess of  which  passes  into  a  dentinal  fibre.  The  odonto- 
blasts proper  are  concerned  in  the  production  of  the 
dentinal  matrix,  according  to  some  by  a  continuous 
growth  of  the  distal  or  outer  part  of  the  cell  and  a 
petrification  of  this  increment,  according  to  others 
by  a  secretion  by  the  cell  of  the  dentinal  matrix. 
Waldeyer,  Tomes,  and  others  consider  the  odonto- 
blasts proper  concerned  in  the  production  both  of  the 
dentinal  matrix  and  dentinal  iibres.  The  odontol)lasts 
proper  and  the  spindle-shaped  cells  are  continuous 
with  the  branched  cells  of  the  pulp  matrix. 

224.  Devolopiiieiit  of  teetli. — The  first  rudi- 
ment of  a  tooth  in  the  embryo  appears  as  early  as  the 
second  month.  It  is  a  solicl  cylindrical  prolongation 
of  the  stratified  epithelium  of  tlie  surface  into  the 
depth  of  the  embryonic  mucous  membrane.  Along  the 
border  of  the  jaws  the  epithelium  appears  thickened, 
and  the  sul>jacent  mucous  membrane  forms  there  a 
depression — the  primitive  dental  groove.  Into  this 
groove  the  solid  cylindrical  prolongation  of  the  surface 
epithelium  takes  place.  This  prolongation  is  the 
Y\\([\mQ\\t  oi  the  enamel  organ.  While  continuing  to 
grow-  towards  the  depth,  it  soon  broadens  at  its  deepest 
part,  and  the  surrounding  vascular  mucous  membrane 
condenses  at  the  bottom  of  the  prolongation  as  the 
rudiment  of  the  tooth  papilla.      While  the  distal  part 


& 


Teeth. 


28r 


of  the  enamel  organ  continues  to  grow  towards  the 
depth,  it  grtidually  embraces  the  tooth  ])apilla  in  the 
shape  of  a  cap — the  enamel  caj)  (Fig  183).  During 
this  time  the  connection  between  the  surface  epithe- 


Fh 


184. — From  a  Section  tlirough  the  Tooth  and  Lower  Jaw  of  Fatal 
Kitten. 


a,  Epithelium  uf  the  free  surface  of  the  gum  {b,  the  raucous  membrane  of  same; 
c,  spongy  bone  of  jaw:  rf,  papilla  of  tooth;  e,  odontoblasts:/,  dentine;  </, 
enamel ;  h,  membrane  of  Nasmy  th  ;  /,  enamel  cells ;  j,  middle  layer  of  enamel 
organ;  A,  outer  layer  of  enamel  organ. 


Hum  and  the  enamel  cap  becomes  greatly  thinned  out 
and  pushed  on  one  side,  owing  to  the  growth  of  the 
enamel  cap  and  papilla  taking  place  chiefly  to  one  side 
of  the  original  dental  groove. 

225.  The  enamel  cap  (Fig.  184)  is  composed  of 
three  strata — an  inner,  middle,  and  outer  stratum. 
The  inner  stratum  is  a  layer  of  beautiful  columnar 
epithelial  cells — the  enamel  cells;  they  were  originally 


2«2 


Elements  of  Histology 


continuous  with  tlie  deep  layer  or  the  columnar  cells 
of  the  surface  e[jithelium.  The  middle  stratum  is  the 
thickest,  and   is  of  great   transparency,    owing    to   a 


a 


\\    '■ 


Fig.  185.— From  a  Vertical  Section  through  Foetal  Tooth  of  Dog.     (^Atlos.") 

a.  Spindle-shaped  cells  of  tbe  tooth  pulp;  b,  the  layer  of  O(lontol)lasts :  c,  the 
ludst  recently  formed  layer  of  dentine;  cl,  older  dentine;  d,  the  layer  of 
enamel  cells;  C'J,  the  enamel ;  e,  outer  cells  of  enamel  organ  ;  /,  tissue  of  the 
tooth  sac. 


transformation  of  the  middle  layer  of  the  epithelial 
cells  into  a  spongy  gelatinous  tissue,  due  to  accumu- 
lation of   fluid    between  the    epithelial    cells    of    this 


Teeth.  283 

layer,  and  to  a  reduction  of  their  substance  to  thin 
nucleated  plates,  apparently  branched.  The  outer 
stratum  consists  of  one  or  more  layers  of  polyhedral 
cells,  continuous  on  tlie  one  hand  with  the  surface 
epithelium  by  the  bridge  of  tlie  rudiment  of  the 
enamel  organ,  and  on  the  other  Nvitli  the  enamel  cells. 

226.  The  foetal  tooth  papilla  is  a  vascular  em- 
bryonic or  gelatinous  tissue  ;  on  its  outer  surface  a 
condensation  of  its  cells  is  soon  noticeable  into  a  more 
or  less  continuous  stratum  of  elongated  or  columnar 
cells,  the  odontoblasts. 

227.  Both  the  dentine  and  enamel  are  developed 
in  connectiou  with  the  odontoblasts  and  the  enamel 
cells  (Fig.  185)  ;  the  former  produce  the  dentine 
on  their  outer  surface,  while  the  latter,  i.e.  the 
enamel  cells,  deposit  the  enamel  on  their  inner 
surface ;  thus  it  happens  that  the  enamel  is  in 
close  contact  with,  and  on  the  outside  of,  the 
dentine.  The  dentine  and  enamel  are  de]josited 
gradually  and  in  layers.  At  first  they  are  soft 
tissues,  showino-  a  vertical  differentiation  corre- 
sponding  to  the  individual  cells  of  the  enamel  cells 
and  odontoblasts  respectively.  Soon  lime  salts  are 
deposited  in  them,  at  first  imperfectly,  but  afterwards 
a  perfect  petrification  takes  place.  The  layer  of  most 
recently  formed  enamel  and  dentine  is  more  or  less 
distinctly  marked  off  from  the  more  advanced  layer, 
the  most  recently  formed  layer  of  the  enauiel  being 
situated  next  to  the  enamel  cells,  that  of  the  dentine 
next  to  the  odontoblasts  (Fig.  186).  The  amount 
of  enamel  and  dentine  formed  is  always  greatest 
in  the  upper  part,  i.e.  that  corresponding  to  the 
future  crown.  The  milk  teeth,  while  continuing 
to  grow,  remain  buried  in  the  mucous  membrane 
of  the  gum,  till  after  hirth  their  proper  time 
arrives,  when  by  active  growth  and  enlai'gement 
they   break   through  the  gum.     During  this  process 


:84 


Elements  of  Histology. 


the  enamel  of  the  crown  remains  co\'ered,  i.p.  carries 
with  it  the  inner  stratum  of  the  enamel  organ  only, 
i.e.  the  enamel  cells  (Fig.  186,  ec)  ;  these,  at  the 
same   time  as   the   surface  of   the  enamel   increases. 


Fig.    18(3.— From  a  Section    through    the    developing    Tooth   of    Kitten. 
(Photograph,  higTibj  magnified.) 

p,  Pulp  of  the  tooth  papilla;  o,  layer  of  odontoblasts  ;  d,  dentine  ;  e,  enamel ;  ec, 
enamel  cells;  w,  middle  layer  of  enamel  organ;  oit,  outer  layer  of  enamel 
organ. 

become  much  flattened,  and,  finally  losing  their  nuclei, 
are  converted  into  a  layer  of  transparent  scales,  the 
membrane  or  cuticle  of  Ncismyth  (Fig.  18-4,  It). 

228.  Long  before  the  milk  tooth  breaks  through 
the  gum,  there  appears  a  solid  cylindrical  mass  of 
epithelial  cells  extending  into  the  depth  from  the 
orifdnal  connection  between  the  enamel  organ  and  the 


Teeth.  285 

epitlielium  of  tlie  surface  of  the  gum  mentioned  above. 
This  new  epitheh'al  outgrowth  represents  the  germ  for 
the  enamel  organ  of  the  permanent  tooth  ;  but  it 
remains  stationary  in  its  growth  till  the  time  arrives 
for  the  milk  tooth  to  be  supplanted  by  a  permanent 
tooth.  Then  that  rudiment  undergoes  exactly  the 
same  changes  of  growth  as  the  enamel  organ  of  the 
milk  tooth  did  in  the  first  j^eriod  of  foetal  life.  A 
new  tooth  is  thus  formed  in  the  depth  of  the  alveolar 
cavity  of  a  milk  tooth,  and  the  growth  of  the  former 
in  size  and  towards  the  surface  gradually  lifts  the 
latter  out  of  its  socket. 

Mummery  has  shown  that  the  dentine  contains 
petrified  fibres  and  traljecuhe,  which  are  direct  con- 
tinuations of  the  pulp  tissue,  and  are  comparable  to 
the  fibres  of  Sharpey  in  bone, 


286 


CHAPTER   XXIV. 

THE      SALIVARY      GLANDS. 

229.     The    salivary    glands,    according    to    tlieir 

structure  and  secretion,  are  of  the  following  kinds  : — 

(1)    True  salivnrif  (Fig.  187),  s^?'o?<5,  or  albuminous 


^v~^^^/i'!u 


Fig.  187. — From  a  Section  througli  a  Serous  or  True  Salivary  Gland  ;  part 
of  the  Human  Submaxillary.    {Atlas.) 

a.  The  gland  alveoli,  lined  with  the  alhuniinous  "  salivary  cells  "  ;  b,  intralobular 
duct  cut  transversely. 

glands,  such  as  the  parotid  of  man  and  mammals, 
the  submaxillary  and  orbital  of  the  rabbit,  the  sub- 
maxillary of  the  guinea-pig.  They  secrete  true,  thin, 
watery  saliva. 


Salivary  Glands, 


287 


230.  (2)  Jfncons  (/lands.  Of  these  there  are  several 
varieties.  In  the  first  phxce,  there  is  the  picre  mucous 
gland  (Fig.  188),  represented  by  the  subUiigual  gland 
of  tlie  guinea-pig  and  many  of  the  simple  buccal  glands 
of   the    mouth.      In    the    next    place^    the    secreting 


Fig.  188.— From  a  Section  through  the   Orhital  (mucous)  Gland  of  Dog. 
Quiescent  State.     (Heidenkain.) 

The  alveoli  are  lined  witli  trans^iiarent  "  mucous  cells,"  and  outside  these  are  the 
demilunes  of  Heidenhain. 


alveolus  may  contain  other  cells  than  true  mucous 
cells  (mucous  (/lands  ivith  deniilunes).  There  may  be 
comparatively  few  of  this  second  variety  of  cell  in  the 
alveolus,  and  such  cells  may  have  an  entirely  peripheral 
position  in  the  alveolus,  and,  being  thus  adapted  in  shape 
to  the  globular  character  of  the  alveolus,  may  become 
flattened  between  the  basement  membrane  and  more 
centrally  disposed  mucous  cells,  so  that  in  section  they 
have  the  appearance  of  half-moon-sha])ed  masses, 
and  are  hence  called  dem.ilutie  cells.  The  alveolus 
may  contain  few  of  these  demilune  cells,  as  in  the 
orbital  or  submaxillary  gland  of  the  dog  (Fig.  188),  or 


288 


Elements  uf  Histology 


a  more  or  less  complete  ring  of  such  cells  may  exist, 
as  in  the  submaxillary  gland  of  the  cat  (Fig.  190). 
Finally,  this  second  variety  of  cell  may  be  so  largely 


Fig.  1S9.— Section  tliruugli  a  Pure  Mucous  Gland  in  the  Resting  State.  The 
nuclei  are  seen  flattened  at  the  iieripliei-y  of  the  alveoli.  The  cells  are 
not  deeply  stained.     There  are  no  demilune  cells.     (Microphotograph.) 


represented  as  to  cause  the  gland  to  be  described  as 
belonging  to  a  separate  variety — mixed  glands. 

231.  (3)  Mixed  salivary,  muco-salivary,  or  sero- 
mucoiis  glands.  Here  some  alveoli  may  be  entirely 
serous,  some  may  belong  to  one  of  the  varieties  of 
so-called  mucous  glands.  Sometimes  the  alveoli  may 
contain  both  serous  and  mucous  cells  similarly 
situated  around  the  lumen,  so  that  we  may  have 
actually  a  mixed  salivary  alveolus  (Fig.  191).  It 
is  justitiable   to    assume  that    demilune    cells    really 


Salivary  Glands. 


289 


represent  occasional  serous  cells  present  in  a  mucous 

alveolus,   and  these  cells  occupy  a  peripheral  position. 

In  addition  to  the  three  salivary  glands— parotid, 

submaxillary,    and    sublingual  — there    are    in    some 


Fig.  190.— Section  througli  the  Submaxillary  Gland  of  Cat.  The  alveoli  are 
in  nearly  all  cases  surrounded  by  a  dark  rim,  composed  of  demilune 
cells.  More  deeply-stained  masses  consisting  of  ducts  are  also  seen. 
{Microphotograph. ) 

cases,  as  in  the  rabbit  and  the  guinea-pig,  two  minute 
additional  glands,  one  intimately  joined  to  the  parotid 
and  the  other  to  the  submaxillary,  and  both  of  the 
nature  of  a  mucous  gland.  These  are  the  superior  and 
inferior  admaxiUary  glands. 

232.  The  framework. — Each  salivary  gland 
is  enveloped  in  a  fibrous  connective-tissue  capsule, 
in  connection  with  which  are  fibrous  trabeculse  and 


290 


Elements  of  Histology 


septa  in  the  interior  of  tJie  gland,  h\  which  the  sub- 
stance of  the  Latter  is  subdivided  into  lobes,  these 
again  into  lobules,  and  these  finally  into  the  alveoli 
or    acini.      The    duct,   large  vessels   and   nerves  pass 


Fig.  191.— Section  tlirougb  a  Human  Submaxillary  Gland.  Nearly  all  the 
alveoli  consist  of  albuminous  cells.  There  is  also  to  be  seen  a  fairly 
large  number  of  somewhat  larger  and  less  deeply-stained  alveoli  which 
consist  largely  of  mucous  cells.     (Microphotograph.) 

to  and  from  the  gland  by  the  hilum.  The  connective 
tissue  is  of  loose  texture,  contains  elastic  filjres,  and,  in 
some  instances  more,  in  others  less,  numerous  lymphoid 
cells.  In  the  sublingual  gland  they  are  so  numerous 
that  they  form  continuous  rows  between  the  alveoli. 
The  connective-tissue  matrix  between  the  alveoli  is 
cliieHy  rejDresented  by  fine  bundles  of  fibrous  tissue 
and  branched  connective-tissue  corpuscles. 


Sal/vanv  Glands.  291 

•1X\.  Tlio  4lii<'l*!i. — Following  the  chief  duct  of 

tlio  ij;l;in(l  thi'oiii;h  tho  liilum  into  tlio  interior,  we  s(;e 
that  it  divides  into  several  larne  branches,  according 
to  the  number  of  lobes ;  each  of  these  takes  up  several 
branches,  one  for  each  lobule.  Following  it  into  the 
lobule,  the  branch  is  very  minute,  and  is  seen  to  take 
up  several  more  minute  tubes  ;  all  these  tubes  within 
the  lobule  are  the  intrnlohidar  chiefs  or  the  salivari/ 
tubes  of  Pliiiger ;  the  bigger  ducts  being  the  inter- 
lohu^ar,  and,  further,  the  interlobar  ducts.  Each  of 
the  latter  consists  of  a  limiting  membrana  propi-ia, 
strengthened,  according  to  the  size  of  the  duct,  by 
thicker  or  thinner  trabecuhe  of  connective  tissue.  In 
the  chief  branches  there  is  present  in  addition  non- 
striped  muscular  tissue.  The  interior  of  the  duct  is 
a  cavity  lined  with  a  layer  of  colunmar  epithelial  cells. 
In  the  largest  branches  there  is,  outside  this  layer  and 
inside  the  membrana  propria,  a  layer  of  small  poly- 
hedral cells. 

234.  The  intralobular  cliicts,  or  the  salivary 
tubes  of  Pliiiger,  have  each  a  distinct  lumen  or  cavity, 
which  is  lined  with  a  single  layer  of  columnar  epithe- 
lium, and  outside  this  is  a  limiting  mend)rana  propria. 
Each  of  the  lining  epithelial  cells  has  a  s})herical 
nucleus  in  about  the  middle  ;  the  outer  half  of  the 
cell  substance  shows  very  marked  longitudinal  stria- 
tion,  due  to  more  or  less  coarse  tibrilljc  (see  Fig.  187). 
The  inner  half — i.e.  the  one  bordering  the  lumen — is 
granular,  or  oidy  very  faintly  striated.  The  outline 
of  these  salivary  tubes  is  never  smooth,  but  irregular — 
i.e.  the  diameter  of  the  tube  varies  from  place  to  ])lace. 

Not  in  all  salivary  glands  do  the  epithelial  cells 
of  the  intralobular  ducts  show  this  coarse  Hbrillation 
in  the  outer  part  of  their  substance — e.g.  it  is 
not  })resent  in  the  sublingual  gland  of  the  dog  or 
the  guinea-pig. 

235.  The   ends  of  the  branches    of    the    salivary 


292  Elements  of  Histology. 

tubes  are  connected  with  the  secreting  parts  of  the 
lobule  —  i.e.  the  acini  or  alveoli.  These  always  very 
conspicuously  differ  in  structure  from  the  salivary 
tubes. 

The  last  part  of  the  duct  which  is  in  immediate 
connection  with  the  alveoli  is  the  intermediate  pcwt, 
this  being  interposed,  as  it  were,  between  the  alveoli 
and  the  salivary  tube  with  librillated  epithelium.  The 
intermediate  part  is  much  narrower  than  the  salivary 
tube,  and  is  lined  with  a  single  layer  of  very  flattened 
epithelial  cells,  each  ^vith  a  single  oval  nucleus  ;  the 
boundary  is  formed  by  the  membrana  propria,  con- 
tinued from  the  salivary  tube.  The  lumen  of  the 
intermediate  part  is  much  smaller  than  that  of  the 
salivary  tube,  and  is  generally  lined  with  a  fine  hyaline 
membrane,  with  here  and  there  an  oblong  nucleus 
in  it. 

At  the  point  of  transition  of  the  salivary  tube 
into  the  intermediate  part  there  is  generally  a  sudden 
diminution  in  size  of  the  former,  and  the  columnar 
cells  of  the  salivary  tube  are  replaced  by  polyhedral 
cells  ;  this  is  the  neck  of  the  intermediate  part ,  In 
some  salivary  glands,  especially  in  the  mucous,  this 
neck  is  the  only  portion  of  the  intermediate  part 
present — e.g.  in  the  submaxillary  and  orbital  glands 
of  the  dog  and  cat,  and  in  the  sublingual  of  the 
rabbit.  In  others,  especially  in  the  serous  salivary 
glands,  as  the  parotid  of  man  and  mammals,  the  sub- 
maxillary of  the  rabbit  and  guinea-pig,  and  in  the 
mixed  salivary — as  the  submaxillary  and  sublingual 
of  man — there  exists  after  the  neck  a  long  inter- 
mediate part,  which  gives  off  several  shorter  or  longer 
branches  of  the  same  kind,  all  ending  in  alveoli. 

236.  The  alveoli  or  aeiiii  are  the  essential  or 
secreting  portion  of  the  gland  ;  they  are  flask-shaped, 
club-shaped,  shorter  or  longer  cylindrical  tubes,  more 
or  less  wavy  or,  if  long,  more  or  less  convoluted ;  many 


Salivary  Glaxds.  293 

of  them  are  branclied.  Generally  several  open  into 
the  same  intermediate  part  of  a  salivary  tube.  The 
acini  are  much  lari^er  in  diameter  than  the  inter- 
mediate ])art.  and  slightly  larger,  or  about  as  large  as 
the  intralobular  ducts.  But  there  is  a  difference  in 
this  respect  between  the  acini  of  a  serous  and  of 
a  mucous  salivary  gland  ;  in  the  former  the  acini 
are  smaller  than  in  the  latter. 

The  membrana  propria  of  the  intermediate  duct 
is  continuous  with  the  membrana  propria  of  the 
acini.  This  is  a  reticulated  structure,  being  in  reality  a 
basket-shai)ed  network  of  hyaline  branched  nucleated 
cells  (Boll).  The  lumen  of  the  acini  is  minute  in  the 
serous,  but  is  larger  in  the  mucous  glands  ;  it  is  in 
both  glands  smaller  during  secretion  than  during  rest. 

237.  The  epithelial  cells  lining  the  acini  are  called 
the  saUi-ary  cells — they  are  of  different  characters  in 
the  different  salivary  glands,  and  chiefly  determine  the 
nature  of  the  gland.  The  cells  are  separated  from  one 
another  by  a  fluid  albuminous  cement  substance, 
(i.)  In  the  serous  or  true  salivary  glands,  as  parotid  of 
man  and  mammals,  submaxillary  of  rabbit  and  guinea- 
pig,  the  salivary  cells  form  a  single  hiyer  of  shorter  or 
longer  columnar  or  pyramidal  albuminous  cells,  com- 
posed of  a  reticulated  protoplasm,  and  containing  a 
spherical  nucleus  in  the  outer  part  of  the  cell,  (ii.) 
In  the  mucous  glands,  such  as  the  sublingual  of  the 
guinea-pig,  or  the  admaxillary  of  the  same  animal,  the 
cells  lining  the  acini  form  a  single  layer  of  goblet- 
shaped  mucous  cells,  such  as  have  been  described 
above.  Each  cell  consists  of  an  inner  principal  part, 
composed  of  a  transparent  mucoid  substance  (contained 
in  a  wide-meshed  reticulum  of  the  protoplasm),  and  of 
an  outer  small,  more  opaque  part,  containing  a  com- 
pressed and  flattened  nucleus.  This  part  is  drawn 
out  in  a  fine  extremity,  which,  being  curved  in  a 
direction    parallel   to    the    surface   of  the    acinus,    is 


294  Elements  of  Histology. 

imbricated  on  its  neighbours.  In  the  case  of  tlie  sub- 
maxillary and  orljital  glands  of  the  dog  and  the  sub- 
lingual of  the  rabbit,  there  exist,  in  addition  to  and 
outside  of  the  mucous  cells  lining  the  acini,  but  within 

the  membrana 
propria,  from 
place  to  place 
crescentic 
1  > -r^  masses,  being 
the  demilunes  of 
-.   /:  ^l)  ':  Q,      Ileidenhain,     or 

;  \;  .     '    Tl   ■' ^^      the    crescents    of 

■  •  .'  ^'  ,  '7  .  ^^-  •  ^  J  ji>:;  Gianuzzi  (see 
'i-^i-J-  'l-:'^  '  -^  -f  Fig.  188).  Each 
0    ^  ^^    "^     V,    _     '^  is     composed    of 

>'    '- A  il-' -■;^^^  ::     ^"1         several     polyhe- 
dral      granular- 


r--'(vi 


f 


\VT 


^  -    .  ->  ^  , •„^.-v  lookmor         cells, 

\^>§^' ^       -^-r-   ■  O  ^^-  each       with       a 

Fig.  192.— From  a  Section  through  the  Orbital      spherical  IIU- 

Gland  of  Dog,  after  prolonged  electrical  Stimu-      „i„„„  .      j.i,p    ppil^ 
lation.    The  acini  are  lined  with  small  granular     ^it;u^5  ,      tiic    ccjio 

cells.    (Lavdovsid.)  "  at    the     margin 

of  the  crescent 
are,  of  course,  thinner  than  those  forming  the  middle. 
Heidenhain  and  his  pupils,  Lavdovski  and  others, 
have  shown  that,  during  prolonged  exhausting 
stimulation  of  the  submaxillary  and  orbital  of  the 
dog,  all  the  lining  cylindrical  mucous  cells  become 
ref)laced  by  small  polyhedral  cells,  similar  to  those  con- 
stituting the  crescents,  while  at  the  same  time  the  acini 
become  smaller  (Fig.  192).  These  observers  maintain 
that  this  change  is  due  to  a  total  destruction  of  the 
mucous  cells,  and  a  replacement  of  them  by  new  ones, 
derived  by  multiplication  from  the  crescent  cells.  This 
is  improbable,  since  during  ordinary  conditions  of  secre- 
tions there  is  no  disappearance  of  the  mucous  cells  as 
such ;   they  change   in   size,    becoming   larger  during 


Salifakv  Glands.  295 

secretion,  and  tboir  contonts  are  converted  into  perfect 
mucus.  It  is  prol)able  that,  on  prolonged  exhaustive 
stimulation,  the  mucous  cells  collapse  into  the  small 
cells,  seen  by  Heidenliain  and  his  pupils. 

238.  (iii.)  The  acini  of  the  sublingual  of  the  dog 
are  again  different  in  structure  both  from  those  of  the 
submaxillary  of  the  dog  and  of  the  sublingual  of  the 
guinea-pig,  for  the  acini  are  there  lined  either  with 
mucous  cells  or  with  columnar  albuminous  cells,  or 
the  two  kinds  of  cells  follow  one  another  in  the  same 
alceolus. 

This  gland  is  a  sort  of  intermediate  form  between 
the  sul)lingual  of  man  and  the  submaxillary  of  man 
and  ape  (Fig.  191).  These  are  the  mixed  or  muco- 
salivary  glands.  In  these  the  great  number  of  acini 
are  serous— ■i.e.  small — with  small  lumen,  and  lined 
with  albuminous  cells,  whereas  there  are  always  present 
a  few  acini  exactly  like  those  of  a  mucous  gland.  The 
two  kinds  of  acini  are  in  direct  continuity  with  one 
another.  In  some  conditions  there  are  only  very  few 
mucous  acini  to  be  met  with  within  the  lobule — -so  few 
sometimes  that  they  seem  to  be  altogether  absent  ;  in 
others  they  are  numerous,  but  even  under  most 
favourable  conditions  they  form  only  a  fraction  of 
the  number  of  the  serous  acini.  In  the  sublingual  of 
man  they  are  much  more  frequent,  and  for  this  reason 
this  gland  possesses  a  great  resemblance  to  the  sub- 
lingual of  the  dog. 

What  appear  to  be  crescents  in  the  mucous  acini 
of  the  human  gland  are  an  oblique  view  of  albuminous 
cells  lininof  the  acini  at  the  transition  between  the 
mucous  and  serous  part  of  the  same  gland-tube. 

239.  The  columnar  salivary  cells  lining  the  acini 
of  the  submaxillary  of  the  guinea-pig  in  some  condi- 
tions show  two  distinct  jjortioiis :  an  outer  homogeneous 
or  slightly  and  longitudinally  striated  substance,  and 
an  inner,  more  transparent,  granular-looking  part,  and 


296 


Elements  of  Histology. 


in  this  respect  the  cells  resemble  those  of  the  pancreas. 
{See  pp.  330-2.) 

240.  Langley  has  shown  (Fig.  193)  that  during 
the  period  preparatory  to  secretion  the  cells  lining 
the  acini  of  the  serous  salivary  glands  become  en- 
larged and  tilled  with  coarse  granules  :  during 
secretion  these  granules  become  used  up,  so  that  the 


Fig.  193. — Acini  of  Serous  Gland.     (Langley.) 
A,  At  rest  ;  B,  first  stage  of  secretion  ;  c,  prolonged  secretion. 


cell-substance  grows  more  transparent,  beginning  from 
the  outer  part  of  the  cell  and  gradually  advancing 
towards  the  lumen  of  the  acini.  These  granules  may 
be  seen  in  the  fresh  gland,  but  reagents  very  rapidly 
destroy  them.  Salivary  glands  hardened  by  the 
usual  reagents,  though  not  themselves  showing  the 
granules,  may,  however,  present  appearances  corre- 
sponding to  the  removal  of  the  granules  from  the 
outer  zone  of  the  alveolus.  It  is  found  that  in 
such  cases  the  outer  zone  stains  more  deeply 
(Fig.  102),  an  appearance  frequently  met  with  in  the 
pancreas. 

AYhen  the  outer  part  of  the  alveolus  is  devoid 
of  granules,  the  alveolus  is  said  to  be  active  or 
partially  exhausted;  when  the  granules  reach  practi- 
cally to  the  outermost  part  of  the  cells,  the  alve- 
olus is  said  to  be  resting.     Under  normal  conditions 


Salivary  Glands.  297 

secretion  in  the  salivary  glands  never  approaches  ex- 
haustion, though  in  the  pancreas  it  is  not  uncommonly 
the  case. 

241.  Blood-vossels    and    lyiiiplialics.— The 

lobules  are  richly  supplied  with  blood-vessels.  The 
arteries  break  up  into  numerous  capillaries,  which 
with  their  dense  networks  surround  and  entwine  the 
acini.  Between  the  interalveolar  connective  tissue 
carrying  the  capillary  blood-vessels  and  the  membrana 
ju'opria  of  the  acini  exist  lymi^h  spaces  surrounding 
the  greater  part  of  the  circumference  of  the  acini 
and  forming  an  intercommunicating  system  of  spaces. 
They  open  into  lymi-iliatic  vessels  accomjoanying  tlie 
intralobular  ducts,  or  at  the  margin  of  the  lobule 
directly  empty  themselves  into  the  interlobular 
lymphatics.  The  connective  tissue  between  the  lobes 
contains  rich  plexuses  of  lymphatics. 

242.  The  iierve-braiiclies  form  plexuses  in  the 
interlobular  tissue.  In  connection  with  them  are 
larger  or  smaller  ganglia  (Fig.  168).  They  are  very 
numerously  met  with  in  the  submaxillary,  but  are 
absent  in  the  parotid.  Some  ganglia  are  present  in 
connection  with  the  nerve-branches  surrounding  the 
chief  duct  of  the  suljlingual  gland. 

Pfliiger  maintains  that  the  ultimate  nerve  fibres 
are  connected  with  the  salivary  cells  of  the  acini  in 
man  and  mammals,  but  this  remains  to  be  proved. 


298 


CHAPTER  XXV. 

THE  MOUTH,  PHARYNX  AND  TONGUE. 

2-43.  The  jflaiids.— Into  the  cavity  of  the 
mouth  and  pharynx  open  very  numerous  minute 
glands,  which,  as  regards  structure  and  secretion, 
are  either  serous  or  mucous.  The  latter  occur  in 
the  depth  of  the  mucous  membrane  covering  the 
U[)S,  in  the  ]:)uccal  mucous  membrane,  in  that  of  the 
hard  palate,  and  especially  in  that  of  the  soft  palate 
and  the  uvula,  in  the  depth  of  the  mucous  membrane 
of  the  tonsils,  at  the  Ijack  of  the  tongue,  and  in  the 
raucous  membrane  of  the  pharynx.  The  serous 
glands  are  found  in  the  back  of  the  tongue,  in  close 
])roximity  to  the  parts  containing  the  special  organs 
for  the  perception  of  taste — the  taste  goblets  or  buds 
(see  below).  All  the  glands  are  very  small,  but 
when  isolated  the}^  are  perceptible  to  the  unaided  eye 
as  minute  whitish  specks,  as  big  as  a  pin's  head,  or 
bigger.  The  largest  are  in  the  lips,  at  the  back  of 
the  tongue  and  soft  palate,  where  there  is  something 
like  a  grouping  of  the  alveoli  around  the  small  branches 
of  the  duct,  so  as  to  form  little  lobules. 

244.  The  chief  duct  generally  opens  with  a  narrow 
mouth  on  the  free  surface  of  the  oral  cavity ;  it 
passes  in  a  vertical  or  oblique  direction  through  the 
superficial  part  of  the  mucous  membrane.  In  the 
deeper,  looser  part  (submucous  tissue)  it  branches 
in  two  or  more  small  ducts,  which  take  up  a  number 
of  alveoli.  Of  course,  on  the  number  of  minute  ducts 
and  alveoli  depends  the  size  of  the  gland. 


Mouth,  Pharyxx  and  Tongue. 


299 


In  man,  all  ducts  are  lined  with  a  single  layer  of 
columnar  epitliclial  cells,  longer  in  the  larger  than 
in  the  smaller  ducts  ;  in  mammals  the  epithelium 
is  a  single  layer 
of  polyhedral  cells. 
No  fibril  lation  is 
noticeable  in  the 
epithelial  cells.  At 
the  transition  of  the 
terminal  ducts  into 
the  acini  there  is 
occasionally  a  slight 
enlargement,  called 
the  infundibuhtm  ; 
here  the  granular- 
looking  epithelial 
cells  of  the  duct 
change  into  the  co- 
lumnar transparent 
mucous  cells  lining 
the  acini. 

245.  The  acini 
of  these  glands  are 
identical  with  those 
of  the  mucous  glands 
described  above  (Fig. 
194) — e.g.  the  sub- 
lingual gland  as  regards  size,  tubular  branched  nature, 
the  lining  epithelium,  and  lumen. 

In  some  instances  (as  in  the  soft  palate  and 
tongue)  the  duct  neir  the  opening  is  lined  with 
ciliated  columnar  epithelium.  The  stratified  epithelium 
of  the  surface  is  generally  continued  a  short  distance 
into  the  mouth  of  the  duct. 

246.  The  serous  glands  at  the  root  of  tlie 
tongue  (von  Ebner)  differ  from  the  mucous  chiefly 
in  the  epithelium,  size,  and  lumen  of  the  acini.    These 


Fig.  194. — Part  of  a  Lobule  of  a  Mucous 
Gland  iu  the  Tongue  of  Dog.     {Atlas.) 

«,  Gland  tubes  (alveolii  viewed  in  various 
directions :  they  are  lined  with  transparent 
■'mucous  ceils"  ;  d,  duct  lined  with  small 
polyhedral  cells. 


300  Elements  of  Histology. 

are  of  exactly  the  same  nature  and  structure  as  those 
of  the  serous  or  true  salivary  glands. 

247.  Saliva  obtained  from  the  mouth  contains 
numbers  of  epithelial  scales  detached  from  the  surface 
of  the  mucous  membrane,  groups  of  bacteria  and 
micrococci,  and  lymph  corpuscles.  Some  of  these  are 
in  a  state  of  disintegration,  while  others  are  swollen 
up  by  the  water  of  the  saliva.  In  these  there  are 
contained  numbers  of  granules  in  rapid  oscillation, 
called  Brownian  molecular  movement. 

248.  The  mucous  nionibrane  lining  the  cavity 
of  the  mouth  consists  of  a  thin  membrane  covered 
on  its  free  surface  with  a  thick  stratified  pavement 
epithelium,  the  most  superficial  cells  being  scales, 
more  or  less  changed  into  horn. 

Underneath  the  epithelium  is  a  somewhat  dense 
feltwork  of  fibrous  connective  tissue,  with  numerous 
elavstic  fibrils  in  networks.  This  part  is  the  corium  or 
mucosa,  and  it  projects  into  the  epithelium  in  the 
shape  of  cylindrical  or  conical  papilla. 

According  to  the  thickness  of  the  epithelium,  the 
papillae  differ  in  length.  The  longest  are  found  where 
the  epithelium  is  thickest — e.g.  in  the  mucosa  of  the 
lips,  soft  palate,  and  vivula. 

Numerous  lymph  corpuscles  are  found  in  the 
mucosa  of  the  palate  and  uvula.  Sometimes  they 
amount  to  diffuse  adenoid  tissue.  The  deeper  part  of 
the  mucous  membrane  is  the  suhmucosa.  It  is  looser 
in  its  texture,  but  it  also  is  composed  of  fibrous  con- 
nective tissue  with  elastic  fibrils.  The  glands  are 
here  embedded ;  adipose  tissue  in  the  shape  of  groups 
of  fat  cells  or  continuous  lobules  of  fat  cells  are  here 
to  be  met  with.  The  large  vascular  and  nervous 
trunks  pass  to  and  from  the  sub  mucosa. 

249.  Striped  uiiiscular  tissue  is  found  in 
the  submucosa.  In  the  lips,  soft  palate,  uvula,  and 
palatine  arches  it  forms  a  very  conspicuous  portion  : 


Mouth ^  Pharynx  and  Tongue. 


301 


namely,  the  sphincter  orbicularis,  with  its  outrunners 
into  the  mucous  membrane  of  the  lips,  the  muscles  of 
the  })alate,  uvula  (levator  and  tensor  palati),  and  the 
arcus  palato-pharyngeus  and  palato-glossus. 

250.  The  last  branches  of  the  arteries  break  up  in 


Fig.  195.— Section  through  the  Tongue  of  Cat ;  the  Blood-vessels  injected. 
The  lower  part  of  the  figure  shows  the  injected  muscular  tissue,  in  the 
middle  part  the  mucous  membrane  with  large  vessels  ;  the  ui)per  part 
shows  the  papillae  filiformes,  with  their  capillary  blood-vessels. 
(Photograph  by  Mr.  A.  Priiuilc.) 


a  dense  capiUary  net  1  cork  on  the  surface  of  the  mucosa, 
and  from  it  loops  ascend  into  the  papillae.  Of  course, 
fat  tissue  glands  and  muscular  tissue  receive  their 
own  supply.  There  is  a  very  rich  i^lexus  of  veins  in 
the  superficial  part  of  the  mucosa.  They  are  con- 
spicuous by  their  size  and  the  thinness  of  their  wall. 


302  Elements  of  Histology. 

Tlie  lymjohatics  form  networks  in  all  layers  of  the 
mucosa,  including  the  papilla^.  The  large  efferent 
trunks  are  situated  in  the  submucosa.  The  last  out- 
runners of  the  nerve-hranches  form  a  j^^^^ris  of  notv- 
meduUated  fibres  in  the  superficial  layer  of  the  mucosa, 
whence  numerous  primitive  fihrilUe.  ascend  into  the 
epithelium  to  form  networks.  Meissner's  tactile  cor- 
puscles have  been  found  in  the  papillae  of  the  lips  and 
in  those  of  the  tongue. 

251.  In  the  pharynx  the  relations  remain  the 
same,  except  in  the  upper  or  nasal  part,  where  we 
find  many  places  covered  with  columnar  ciliated 
epithelium.  As  in  the  palatine  tonsils,  so  also  here, 
the  mucosa  is  infiltrated  with  difiiise  adenoid  tissue, 
and  with  lymph  follicles  in  great  numbers.  This  forms 
the  pJuiryngeal  tonsil  of  Luschka. 

In  the  palatine  tonsil  and  in  the  pharyngeal  tonsil 
there  are  numerous  crypts  leading  from  the  surface 
into  the  depth.  This  is  due  to  the  folding  of  the  in- 
filtrated mucosa.  Such  crypts  are,  in  the  pharynx, 
sometimes  lined  all  through  with  ciliated  epithelium, 
although  the  parts  of  the  free  surface  around  them 
are  covered  with  stratified  pavement  epithelium. 

252.  The  tongue  is  a  fold  of  the  mucous  mem- 
brane. Its  bulk  is  made  up  of  striped  muscular  tissue 
(genio-,  hyo-,  and  stylo-glossus ;  according  to  direction: 
longitudinalis  superior  and  inferior,  and  transversus 
lingupe).  The  lower  surface  is  covered  with  a  delicate 
mucous  membrane,  identical  in  structure  with  that 
lining  the  rest  of  the  oral  cavity,  whereas  the  upper 
part  is  covered  with  a  membrane,  of  which  the  mucosa 
projects  over  the  free  surface  as  exceedingly  numerous 
fine  and  short  hairdike  processes,  the papiUct  jilijormes, 
or  as  less  numerous,  isolated,  somewhat  longer  and 
broader  mushroom-shaped  papiUce  fungiformes.  The 
papilla?,  as  well  as  the  pits  between  them,  are  covered 
with  stratified  pavement  epithelium.   Each  has  numbers 


MOUTH^    F/fARVNX  AND    ToNCUE. 


;o3 


of  minute  secondary  papillne.  Their  substance,  like 
the  mucous  membrane  of  the  tongue,  is  made  up  of 
fibrous  connective  tissue.  Tlie  mucous  membrane  is  on 
the  whole  thin,  and  is  firmly  and  intimately  connected 


/*»»!». 


Fig.  196. — Section  through  the  Papilla  Foliata  of  Rabbit,  showiug  the  Taste 
Buds  amongst  the  Epithelium.     In  the  depth  are  Imndles  of  muscular 
libres  and  glands.      Magnifying  power,    40.     {Photograph  by   Mr.   A 
Pringlc.) 

with  the  fil3rous  tissue  forming  the  septa  between  the 
muscular  bundles  of  the  deeper  tissue.  It  contains 
large  vascular  trunks,  amongst  which  the  plexus  of 
veins  is  very  consj^icuous  (Fig.  195).  On  the  surface  of 
the  mucosa  is  a  rich  network  of  capillary  blood-vessels, 
extending  as  complex  loops  into  the  papillse.  Lym- 
phatics form  rich  plexuses  in  the  mucosa  and  in  the 
deep    muscular    tissue.     Adipose   tissue   is    common 


104 


Elements  of  Histology. 


between  the  muscular  bundles,  especially  at  the  back 
of  the  toncfue. 

253.  There  are  two  varieties  of  glands  present  in 
the  tongue,  the  mucous  and  serous.  The  latter  occur 
only  at  the  back,  and  in  the  immediate  neighbourhood 


Fig.  197.— Section  through  Taste  Organ  (Papilla  Foliata.)  From  same 
preparation  as  Fig.  196,  more  magnitied,  to  show  the  taste  buds. 
{Photogrcq^h  by  Mr.  A.  Pringle.) 


of  the  taste  organs ;  the  mucous  glands  are  chiefly 
present  at  the  back  ;  but  in  the  human  tongue  there 
are  small  mucous  glands  (glands  of  Xuhn)  at  the  tip. 
All  the  glands  at  the  back  are  embedded  between  the 
bundles  of  striped  muscular  tissue,  and  thus  the  move- 
ments of  the  tongue  have  the  effect  of  squeezing  out 
the     secretion    of    the    glands.     About    the 


glands 


Mouth,  Pharynx  and  Tongue.  305 

numerous   nerve  bundles  are  found  connected  with 
minute  ganglia. 

At  the  root  of  the  tongue  the  mucous  membrane  is 
much  thicker,  and  contains  in  its  mucosa  numerous 
lymph  follicles  and  diffuse  adenoid  tissue.  Thus 
numerous  knob-like  or  fold-like  prominences  of  the 
mucosa  are  produced.  There  are  also  minute  pits  or 
crypts  leading  into  the  depth  of  these  prominences. 

254.  The  psipilltii!  circiiiiivallatae  are  large 
papill?e  fungiformes,  each  surrounded  by  a  fold  of  the 
mucosa.  They  contain  taste  goblets  or  buds — i.e.  the 
terminal  taste  organs.  At  the  margin  of  the  tongue, 
in  the  region  of  the  circumvallate  papillae,  there  are 
always  a  few  permanent  folds,  which  also  contain  taste 
goblets.  In  some  domestic  animals  these  folds  assume 
a  definite  organisation — e.g.  in  the  rabbit  there  is  an 
oval  or  circular  organ  composed  of  numbers  of  parallel 
and  permanent  folds,  jiainlla  foliata  (Fig.  196). 

255.  The  papillae  fungiformes  of  the  rest  of  the 
tongue  also  contain  in  some  places  a  taste  goblet.  But 
most  of  the  taste  goblets  are  found  on  the  papilla?  circum- 
vallatae  and  foliatse.  In  both  kinds  of  structures  the 
taste  goblets  are  placed  in  several  rows  close  round 
the  bottom  of  the  pit,  separating,  in  the  papillae 
circumvallatae,  the  papillae  fungiformes  from  the  fold 
of  the  mucosa  surrounding  it  :  in  the  papilla  foliata 
the  pits  are  represented  by  grooves  separating  the 
individual  folds  from  one  another. 

256.  The  taste  jfoblets  or  taste  buds  are 
barrel- or  llask-shaped  structures  (Fig.  197)  extending 
in  a  vertical  direction  through  the  epithelium,  from  the 
free  surface  to  the  mucosa.  Each  is  covered  with  flat- 
tened, elongated  epithelial  cells,  forming  its  periphery  ; 
these  are  the  tegmental  cells.  The  interior  of  the  goblet 
is  made  up  of  a  bundle  of  spindle-shaped  or  staff-shaped 
taste  cells.  Each  includes  an  oval  nucleus,  and  is 
drawn  out  into  an  outer  and  an  inner  fine  extremity. 

u 


;o6 


Elements  of  Histology. 


The  former  extends  to  the  free  surface,  projecting  just 
through  the  mouth  of  the  goblet,  and  resembles  a  tine 
hair ;  the  latter  is  generally  y)ranched,  and  passes 
towards  the  mucosa,  where  it  probably  becomes 
connected  with  a  nerve  fibre.  The  mucosa  of  these 
parts  contains  rich  plexuses  of  nerve  fibres. 

Accordmtr  to  Eetzius  the  meduUated  nerve  fibres 


Pig.  198.— Ending  of  Nerve  Fibres  in  and  around  Taste  Buds  of  Rabbit.  {G. 

SetziiiSffrom  Quain.) 
n,  Xerve  fibres;  5.  taste  bud  ;  i,  iutrabulbar  ramification  of  nerve  fibrils;  p, 

peribulbar  ramification  of  nerve  fibrils  ;  s,  sulcus  between  two  adjacent  folds 

of  the  papilla  f  oliata. 

entering  from  the  mucosa  lose  their  medullary 
sheath  and  continue  their  course,  either  as  peribulbar 
ramifications  between  the  tegmental  cells,  or  as  iutra- 
bulbar fibres  between  and  amongst  the  taste  cells. 
Both  sets  of  fibres  terminate  with  free  knoblike 
endings  (Fig.  198). 

Into  the  pits  surrounded  by  taste  goblets  open  the 
ducts  of  the  serous  glands  only  (von  Ebner). 


3°  7 


CHAPTER    XXVI. 

THE    (ESOPHAGUS    AND    STOMACH. 

257.  I.  Tlic  €BSO|>liag^ii§. — Beginning  with  the 
cesophagiis,  and  ending  with  the  rectum  of  the  large 
intestine,  the  wall  of  the  alimentary  canal  consists  of 
an  inner  coat  or  mucous  membrane,  an  outer  or 
muscular  coat,  and  outside  this  a  thin  fibrous  coat, 
which,  commencing  with  the  cardia  of  the  stomach,  is 
the  serous  covering,  or  the  visceral  peritoneum. 

The  epithelium  lining  the  inner  or  free  surface  of 
the  mucous  membrane  of  the  oesophagus  is  a  thick, 
stratified,  pavement  epithelium. 

In  Batrachia,  not  only  the  oral  cavity  and 
pharynx,  but  also  the  oesophagus,  are  lined  with 
ciliated  columnar  epithelium. 

The  mucous  membrane  is  a  fibrous  connective- 
tissue  membrane,  the  superficial  part  of  which  is 
dense — the  mucosa;  this  projects,  in  the  shape  of 
small  papillae,  into  the  epithelium. 

The  deeper,  looser  portion  of  the  mucous  membrane 
is  the  suh mucosa  ;  in  it  lie  small  mucous  glands,  the 
ducts  of  which  pass  in  a  vertical  or  oblique  direction 
through  the  mucosa,  in  order  to  open  on  the  free 
surface.  In  man  these  glands  are  comparatively 
scarce ;  in  carnivorous  animals  (dog,  cat)  they  form 
an  almost  continuous  layer  (Fig.  199). 

258.  Between  the  mucosa  and  submucosa  are 
longitudinal  bundles  of  non-striped  muscular  tissue. 
At  the  beginning  of  the  oesophagus  they  are  absent, 
but    soon   make   their   appearance — at  first  as  small 


3o8 


Elements  of  Histology. 


bundles  sejDarated  from  one  another  by  masses  of  con- 
nective tissue  ;  but  lower  down,  about  the  middle, 
thej  form  a  continuous  stratum  of  longitudinal 
bundles.      This  is  the  miiscularis  mucosce  (Fig.  200). 


re-^^*^ 


—^^n 


Fig.  199.— From  a  Longitudinal  Section  througli  the  Mucous  Membrane  of 
the  ffidopliagus  of  Dog.     {Atlo.s.') 

c,  Stratified  pavement   epithelium  of  the    surface;   m,  muscularis  mucosa; 
between  the  two  is  the  mucosa ;  g,  mucous  irlands  ;  d,  ducts  of  same. 

Outside  the  submucosa  is  the  muscularis  externa. 
This  consists  of  an  inner  thicker  circular  and  an  outer 
thinner  loncjitudinal  coat.  And  outside  this  is  the 
outer,  or  limiting,  fibrous  coat  of  the  oesophagus.  In 
man  the  outer  muscular  coat  consists  of  non-striped 
muscular  tissue,  except  at  the  beginning  (about  the 
upper  third,  or  less)  of  the  oesophagus,  which  is 
composed    of    the    striped    variety ;    but    in    many 


(Esophagus. 


309 


mammals  almost  the  whole  of  the  external  muscular 
coat,  except  the  part  nearest  the  cardia,  is  made  up  of 
stripe*  I  tihres. 

259.  The  large  vessels  pass  into   the  submucosa, 


Fig.  200. — Ti'ansverse  Section  through  the  (Esophagus  of  a  Newly-born 
Child.     {Photograph.    Lovj  magnification.) 

1,  Stratified  epillieliura  of  the  inner  surface;  2,  mucosa  containing  cross-cut 
hundles  of  non-striped  muscle,  muscularis  raucoss  ;  3,  outer  muscular  coat. 

whence  their  liner  branches  pass  to  the  surface  parts. 
The  superficial  part  of  the  mucosa  and  the  papillae 
contain  the  capillary  networks.  The  outer  muscular 
coat  and  the  muscularis  mucosae  have  their  own 
vascular  supply. 

There  is  a  rich  plexus  of  lymphatics  in  the  mucosa, 
and  this  leads  to  a  plexus  of  larger  vessels  in  the 
submucosa    ^Teichmann).        The    nerves    form    rich 


3IO  Elements  of  Histology. 

plexuses  in  the  outer  fibrous  coat ;  these  plexuses 
include  numerous  ganglia.  A  second  plexus  of  non- 
medullatecl  fibres  lies  between  the  longitudinal  and 
circular  muscular  coat ;  a  few  ganglia  are  connected 
with  this  plexus.  In  the  submucosa  are  also  plexuses 
of  non-medullated  fibres.  Now  and  then  a  small 
ganglion  is  connected  also  with  this  plexus. 

260.  II.  The  istoniacli. — Beginning  with  the 
cardia,  the  mucous  membrane  of  the  stomach  is  covered 
with  a  single  layer  of  beautiful  thin  columnar  epithelial 
cells,  most  of  which  are  mucus-secreting  goblet  cells. 
On  the  surface  of  the  mucous  membrane  of  the  stomach 
open  numerous  fine  ducts  of  glands,  placed  very  closely 
side  by  side.  These  extend,  more  or  less  vertically,  as 
minute  tubes,  into  the  depth  of  the  mucous  membrane. 
In  the  pyloric  end,  where  the  mucous  membrane 
presents  a  pale  aspect,  the  glands  are  called  the  i^yloric 
glands  :  in  the  rest  of  the  stomach,  the  mucous 
membrane  presents  a  reddish  or  red-brown  appearance, 
and  here  the  glands  have  a  different  character.  This 
second  variety  of  gland  is  typical  of  the  cardiac  end 
of  the  stomach  as  distinct  from  the  pyloric,  and  hence 
is  described  as  the  cardiac  gland. 

261.  The  part  of  the  mucous  membrane  containing 
the  glands  is  the  mucosa ;  outside  this  is  a  loose 
connective  tissue  containing  the  large  vessels — this 
is  the  submucosa.  Between  the  two,  but  belonging  to 
the  mucosa,  is  the  muscularis  mucosce,  a  thick  stratum 
of  bundles  of  non- striped  muscular  tissue,  arranged 
in  most  parts  of  the  stomach  as  an  inner  circular  and 
an  outer  longitudinal  layer.  The  tissue  of  the  mucosa 
contains  the  gland  tubes,  arranged  more  or  less  in 
small  groups.  Between  them  is  a  delicate  connective 
tissue,  in  which  the  minute  capillary  blood-vessels 
pass  in  a  direction  vertical  to  the  surface.  Numerous 
small  l)undles  of  non-striped  muscular  fibres  pass  from 
the    muscularis    mucosae    towards     the    surface — up 


Stomach. 


;ii 


to  near  the  epitheliuin  of  the  surface — forming 
longitudinal  muscular  sheaths,  as  it  were,  around 
the  gland  tubes. 

The  plicce   villos?e  of  the   suj)erficial   part  of  the 


Fig.  201.— Cardiac  Glands. 

A,  Under  a  low  power  ;  d,  duct ;  n^  neck,  b,  part  of  the  fundus  of  a  gland  tube 
under  a  high  power  ;  Pi  parietal  cells ;  c,  chief  cells. 


mucosa  contain  fibrous  connective  tissue  and  numerous 
lymphoid  cells. 


312  Elements  of  Histology. 

262.  The  car<liac  g'laiicls  (Fig.  201)  are  more 
or  less  wavy  tubes,  extending  down  to  the  mnscularis 
mucosae.  The  dee})  part  is  broader  than  the  rest,  and 
is  more  or  less  curved,  seldom  branched.  This  is  the 
-fundus  of  the  gland  ;  near  the  surface  of  the  mucosa 
is  the  thinnest  part  of  the  tube  ;  this  is  the  neck. 
Two  or  three  neighbouring  glands  may  join  and  open 
into  a  short  cylindrical  duct.  The  duct  is  lined  with 
a  layer  of  columnar  ej)ithelial  cells,  continuous  and 
identical  wdth  that  covering  the  free  surface  between 
contiguous  glands.  The  duct  may  be  really  represented 
by  a  shallow  depression  from  the  surface ;  it  is  then 
more  usual  to  speak  of  the  mouth  of  the  gland. 

263.  The  epithelium  covering  the  surface  consists 
of  mucous  cells.  The  outer  two-thirds  stain  very 
slightly  as  a  rule,  the  nucleus  is  oval  and  situated  in  the 
inner  third  of  the  cell,  where  the  cell  substance  stains 
more  deeply.  At  the  base  of  these  cells  more  deeply 
staining  rejjlacement  cells  may  be  seen.  The  neck 
and  fundus  of  the  cardiac  gland  is  made  up  of  two 
kinds  of  cells.  The  first  variety  occupies  in  general  a 
more  central  position  around  the  lumen,  the  cells  are 
as  a  rule  very  indistinct  in  their  outlines,  the  nucleus 
is  in  the  outer  half  of  the  cell  and  usually  somewhat 
shrunken.  These  cells  are  usually  spoken  of  as  the 
central,  i-)ei')tic,  or  c/n'e/ cells.  The  shape  of  these  cells 
is  cubical  or  short  columnar.  The  other  variety  of 
cell  is  characterised  by  a  more  peripheral  position — at 
any  rate,  in  the  fundus  of  the  gland,  their  outlines  are 
much  more  distinct ;  the  nucleus  is  oval  and  situated 
in  the  centre  of  the  cell.  These  cells  may  impinge  on 
the  lumen  at  the  neck  of  the  gland,  where  they  are 
most  numerous ;  in  the  fundus  they  are  scattered  and 
placed  between  the  investing  membrane  and  the 
central  cells.  These  cells  are  spoken  of  as  jjarietcd, 
oxijntic,  or  ovoid  cells.  The  cardiac  glands  may 
present    appearances    showing    the    secretion   in    the 


Stomach. 


13 


condition  of  granules  in  the  cells.  Granules  are 
observable  ])oth  in  the  parietal  and  central  cells ; 
they  are  more  conspicuous  and  more  easily  j^reserved 
in  the  latter. 

264.  The  pyloric  g^laiids  (Fig.  202).— Thec^t^c^ 


iM 


Fig.   202.— Vertical  Section  through  the  Pyloric  Region  of  the  Gastric 
Mucous  Membrane.     (Microphotogrcq^h.) 

The  wide  funnel-shaped  mouths  are  seen  at  the  level  M,  the  twisted  ends  cut 
across  in  various  planes  at  level  f;  the  darkish  band  at  level  m.m.  is  the 
niuscularis  mucosse  ;  s.m.,  submucous  layer. 

of  each  pyloric  gland  is  several  times  longer  than  that  of 
the  cardiac.  The  duct  of  the  former  occupies  in  some 
places  as  much  as  half  of  the  thickness  of  the  mucosa, 
whereas  that  of  the  latter  does  not  exceed,  in  the 
fundus  of  the  stomach  or  in  the  cardia,  more  than  one- 
fourth  or  one-fifth  of  the  thickness. 


314  Elements  of  Histology. 

The  epithelium  lining  the  duct  of  the  pyloric 
glands  is  similar  to  that  of  the  free  surface.  Several 
tubes  open  into  one  duct  by  a  short  neck.  The 
fundus  or  tube  is  much  convoluted  and  generally 
branched.       It  is  lined  by   only  one  variety  of  cell, 


Fig.  203. — From  a  Section  throngli  the  Transition  of  the  Pj'lorus  into  the 
Duodenum.     (Micwphotograjyh.     Lov:  poicer.) 

a.  Duodenal  mucous    membrane    with    villi ;    ft,  pyloric   mucosa  with  lymph 
follicles  ;  c,  Brunner's  glauds  directly  continuous  with  the  pyloric  glands. 


which  bears  some  resemblance  to  the  central  cell  of 
the  cardiac  glands.  It  is  difficult  to  make  out  any 
appearance  of  granules  either  in  the  fresh  or  hardened 
condition. 

265.  Between  the  mucous  membrane  with  cardiac 
glands  and  the  pyloric  end  of  the  stomach  with  pyloric 


Stomach.  315 

glands  there  is  a  narrow  intermediate  zone,  in  which 
the  cardiac  ghxnds  appear  ])y  degrees  to  merge  into 
the  pyloric  glands.  That  is  to  say,  the  short  duct  of 
the  former  gradually  eloDgates,  the  gland  tubes  get 
shorter  in  proportion  and  convoluted,  their  lumen 
gradually  enlarges,  and  the  parietal  cells  become  fewer 
and  ultimately  disappear. 

266.  The  mucosa  contains  isolated  lymph  follicles, 
the  so-called  glandular  lenticulares  (Fig.  203). 

The  spaces  between  the  glands  themselves  and 
between  the  glands  and  the  muscularis  mucosfe  are 
filled  up  by  a  delicate  connective  tissue  somewhat 
condensed  immediately  around  the  tubes.  Leucocytes 
are  plentiful  in  the  meshes  of  this  network.  One 
particular  variety  of  leucocyte,  the  so-called  basophile 
cell,  may  under  certain  conditions  be  very  conspicuous. 

267.  The  submucosa  is  of  very  loose  texture,  and 
enables  the  mucosa  to  become  easily  folded  in  all 
directions. 

268.  The  muscular  coat  is  very  thick,  and  consists 
of  an  outer  longitudinal  and  an  inner  thicker  circular 
stratum  of  non-striped  muscular  tissue.  Numerous 
oblique  bundles  are  found  in  the  inner  section  of  the 
circular  stratum. 

Tiie  gland  tubes  are  ensheathed  in  a  network  of 
cajnllary  blood-vessels  derived  from  the  arteries  of 
the  submucosa.  This  network  forms  on  the  surface 
a  special  dense  horizontal  layer,  from  which  the  venous 
branches  are  derived.  The  outer  muscular  coat  and 
the  muscularis  mucosae  possess  their  own  vascular 
supply. 

269.  The  lymphatics  form  a  network  in  the 
mucosa  near  the  fundus  of  the  glands.  Into  this 
plexus  lead  lympathics  wdiich  run  longitudinally 
between  the  glands  ;  they  anastomose  with  one 
another  freely,  and  extend  to  near  the  inner  surface 
(Loven).     Another  plexus  is  found  in  the  submucosa. 


3i6  Elements  of  Histology. 

Between  the  longitudinal  and  circular  stratum  of 
the  outer  muscular  coat,  and  extending  parallel  to  the 
surface,  is  a  plexus  of  non-medullated  nerve  branches 
with  a  few  ganglia  in  its  nodes.  This  corresponds  to 
the  flexus  of  Auerhach  of  the  intestine,  and  is  destined 
for  the  outer  muscular  coat.  A  second  plexus  of  non- 
medullated  nerve  branches  with  ganglia  also  extending 
parallel  to  the  surface  lies  in  the  submucosa.  This 
corresponds  to  the  p/e^^s  of  Meiasner  of  the  intestine, 
and  is  destined  for  the  muscularis  mucosae  and  the 
mucosa. 

According  to  Ralje,  the  gastric  gland  tubes  in  the 
horse  are  surrounded  by  a  rich  plexus  of  nerve  fibres, 
terminating  in  peculiar  spindle-shaped  cells. 


M 


CHAPTER   XXVII. 


THE     SMALL     AND    LARGE     INTESTINE. 


270.  The   epithelium  covering  the   inner   or  free 

surface   of  the  mucous   membrane  of  the  small  and 

large  intestine  is  a  single  layer  of  columnar  cells,  their 

protoplasm    more    or    less    distinctly    longitudinally 

a 


/ 


Fig.  204. — Epithelium  covering  the  Surface  of  a  Villus  of  Small  Intestine. 

(Atlas.) 
a.  Striated  free  border  ;  b,  goblet  cell. 

fibrillated  ;  their  free  surface  appears  covered  with 
a  vertically  and  finely  striated  free  border  (Fig.  204). 
Many  cells  are  goblet  cells.  Underneath  the  epithe- 
lium is  a  basement  membrane,  the  sub-epithelial 
endothelium  of  Debove. 

As  in  the  stomach,  so  also  in  the  small  and  large 
intestine,  the  mucosa  is  connected  with  the  outer 
muscular  coat  by  a  loose-textured  fibrous  subrnucosa, 
in  which  lie  the  large  vascular  trunks,  and  in  many 
places  larger  or  smaller  groups  of  fat  cells  and  lymph 
corpuscles.  Between  the  mucosa  and  subrnucosa,  but 


3i8  Elements  of  Histology. 

belonging  to  the  former,  is  a  layer  of  non-striped 
muscular  tissue,  the  muscularls  inucosce.  This  is  in 
many  places  composed  of  inner  circular  and  outer 
longitudinal  bundles,  but  there  are  a  good  many 
places,  especially  in  the  small  intestine,  where  only  a 
layer  of  longitudinal  bundles  can  be  made  out. 

The  tissue  of  the   mucosa  is  similar  in  structure 
to  adenoid  tissue  (Fig.  205),  consisting  of  a  reticular 


Fig.  205. — From  a  Longitudinal   Section  through  a  Villus  of  the  Small 

Intestine. 

«,  Epithelium  of  the  surface;  ft,  non-striped  muscular  fibres.  Immediately 
underneath  the  epithelium  is  a  basement  membrane  with  oblong  nuclei ;  the 
tissue  of  the  villus  is  made  up  of  a  reticulum  of  cells ;  in  its  meshes  are 
lymph  corpuscles. 

matrix  with  flattened  large  nucleated  endotheloid 
cells  and  numerous  lymph  corpuscles.  These  are 
either  small  lymph  corpuscles  like  leucocytes,  or  they 
are  somewhat  larger  and  filled  with  coarse  granules 
— plasma  cells.  The  mucosa  of  the  small  and  large 
intestine  contains  simple  gland  tubes,  the  cryiJts  or 
follicles  of  Lieberkilhn  (Fig.  206)  ;  they  are  placed 
vertically  and  closely  side  by  side,  extending  from  the 
free  surface,  where  they  open,  to  the  muscularis 
mucosae.  These  glands  possess  a  large  lumen,  and  are 
lined  with  a  single  layer  of  columnar  epithelial  cells, 
many  of  them  goblet  cells. 

271.  In  the  small  intestme  the  mucosa  projects 
beyond  the  surface  as  numerous  longer  or  shorter, 
cylindrical,  conical,  or  leaf-shaped  villi  (Fig.  206). 
These    are,    of    course,    covered    with    the    columnar 


Small  and  Large  Intestine. 


319 


epithelium  of  the  general  surface,  and  their  tissue  is  the 
same  as  that  of  the  mucosa — i.e.  adenoid  tissue  (Fig. 
207) — with  the  addition  of:  {a)  One  or  two  central  wide 
chyle  (lymph)  vessels  (Fig.  209),  their  wall  being  a 
single  layer  of  endothelial  plates.       {b)  Along  these 


'V  mM'^ 


Fig.  206.— From  a  Vertical  Section  tlirougli  a  Fold  of  the  Mucous  Mem- 
brane of  the  Jejunum  of  Dog.     (Atlas.) 

c,  Mucosa,  coutaining  the  crypts  of  Lieberkilbn,  and  projecting  as  the  villi; 
in,  muscularis  mucosae ;  s,  submucosa. 

chyle  vessels  are  longitudinal  bundles  of  non-striped 
muscular  tissue,  extending  from  the  base  to  the  apex  of 
the  villus^  terminating  in  connection  with  the  cells  of 
the  basement  membrane — i.e.  the  sub-epithelial  endo- 
thelium, (c)  A  network  of  capillary  blood-vessels  ex- 
tending over  the  whole  of  the  villus  close  to  the 
epithelium  of  the  surface  (Fig.  208).  This  capillary 
network  derives  its  blood  from  an  artery  in  about  the 
middle  or  upper  part  of  the  villus.  Two  venous 
vessels  carry  away  the  blood  from  the  villus. 


320 


Elements  of  Histology. 


The  Lieberkiihn's  crypts  open  between  the  bases 
of  the  villi. 

About  the  base  of  the  villi  of  the  small  intestine, 


Fig.  207. — Transverse  Section  through  Villus  of  Small  Intestine  of  Dog. 
(B.e.idzn'ho.in.) 

Showing  the  columnar  epithelium  lining  the  free  surface,  the  adenoid  tissue 
forniini-'  the  groundwork ;  amongst  the  lymph  cells  of  this  adenoid  tissue 
there  are  numerous  large  cells  filled  with  fat-droplets  ;  the  central  lacteal  as 
also  the  capillary  blood-vessels  are  shown  cut  across. 

and  about  the  base  of  the  plicae  villosas  of  the  stomach 
(p.  311),  there  exist  amongst  the  epithelium  of  the 
surface  peculiar  goblet-shaped  groups  of  epithelial 
cells,  which,  as  AYatney  has  shown,  are  due  to  local 
multiplication  of  the  epithelial  cells. 

272.  Lymph  follicles  occur  singly  in  the  submucosa, 


Small  and  Large  Intestine. 


321 


and  extend  witli  their  inner  part  or  summit  through 
the  muscularis  mucosie  into  the  mucosa  to  near  the 
internal  free  surface  of  the  hitter  (Fig.  209).  These 
are  the  solitary  lymph  foUicIes  of  the  small  and  large 
intestine  ;  in  the  latter  they  are  larger  than  in  the 
former. 

Agminated  glands,  or  Peyers  ylands,  are  larger  or 
smaller  groups  of  lymph  follicles,  more  or  less  fused 
with  one  another, 
and  situated  with 
their  main  part  in 
the  submucosa, 
but  extending 
with  their  summit 
to  the  epithelium 
of  the  free  surface 
of  the  mucosa 
(Fig.  210).  In  the 
lower  part  of  the 
ileum  these 
Peyer's  glands  are 
very  numerous. 
The  epithelium 
covering  the  sum- 
mits   of    these 

lymph  follicles  is  invaded  by,  and  more  or  less 
replaced  by,  the  lymph  corpuscles  of  the  adenoid 
tissue  of  the  follicles  (Watney),  similar  to  what 
is  the  case  in  the  tonsils  [see  par.  124).  Isolated 
]vmph  corpuscles  are  met  witli  amongst  the  epithelium 
also  of  other  parts  of  the  intestine — e.g.  the  epithelium 
covering  the  villi  (Fig.  204). 

The  outer  muscular  coat  consists  of  an  inner  thicker 
circular  and  an  outer  thinner  longitudinal  stratum  of 
non-striped  muscular  tissue. 

In  the  large  intestine,  in  the  "  ligamenta,"  only  the 
longitudinal  layer  is  present,  and  is  much  thickened. 

V 


Fig.  20s.— From  a  Vertical  Section  through  the 
Siual]  Intestine  of  Mouse ;  the  blood-vessels 
are  injected.     (Atlas.) 

The  networks  of  the  capillaries  of  the  villi  are  well 
shown. 


;22 


Elements  of  Histology. 


273.  The  blood-vessels  form  sepaiate  systems  of 
capillaries  for  the  serous  covering,  for  the  outer  mus- 
cular coat,  for  the  muscularis  mucosa?,  and  the  richest 
of  all  for  the  mucosa  with  its  Lieberkiihn's  crypts. 
The  capillary  network  of  the  villi  is  connected  with 
that  of  the  rest  of  the  mucosae  (Fig.  208). 


Fig.  209.— From  a  Section  through  a  part  of  a  Human  Peyers  Patch, 
showing  the  distribution  of  tlie  lynijihatic  vessels  in  the  mucosa  and 
submucosa.    (Frey.) 

a.  Villi,  with  central  chyle  vessel ;  b,  Lieberkiihn's  crypts:  c,  region  of  muscu- 
laris mucosEB :  /,  lymph  follicle ;  g,  network  of  lymphatics  around  the  lymph 
follicle;  I,  lymphatic  network  of  submucosa:  k,  efferent  lymphatic" trunk. 


The  chyle  vessel,  or  vessels  of  the  villi,  commence 
with  a  blind  extremity  near  the  apex  of  the  villi. 
At  the  base  the  chyle  vessel  becomes  narrower  and 
empties  itself  into  a  j^lexus  of  lymphatic  vessels  and 
sinuses  belon^inor  to  the  mucosa,  and  situated  be- 
tween  the    crypts    of    Lieberkiihn  (Fig.  209).       This 


Small  and  Large  Intestink. 


323 


network  is  the  same  both  in  the  small  and  large 
intestine,  as  is  also  that  of  the  lymphatics  of  the 
submucosa  with  which  the  former  communicates.  The 
lymph  follicles  are  generally  surrounded  with  sinuous 
vessels  of  this  plexus.      The    efferent  trunks  of  the 


Fig.  210. — Cross  section  tlinnmh  tiie  C;t'cuiu  of  Rabbit,  sliowiiig  a  Fever's 

ratch.  '     ■ 

(!,  >[iicous  membrane;  b.  summits  of  the  lymph  follicles  reaching  the  free 
surface;  c,  body  of  the  lymph  folliclfs  iu  the  submucous  tissue:  d, outer 
muscular  coat.    {PItoto.    Loic  Maynijication.) 


submucous  plexus,  while  passing  through  the  outer 
muscular  coat  in  order  to  reach  the  mesentery,  take 
up  the  efferent  vessels  of  the  plexus  of  the  lymphatics 
of  the  muscular  coat. 


324  Elements  of  Histology. 

L'74.  The  cliyle,  composed  of  granules  and  fat 
globules  of  different  but  minute  sizes,  passes  from  the 
inner  free  surface  of  the  mucous  membrane  of  the 
small  intestine  through  the  epithelium  into  the  spaces 


Fig.   211.— Vertical  Section  through  the  Mucous  Membrane  of  the  large 
Intestine.     {Micropliotograph.) 

Some  six  elands  are  shown  occupying  almost  the  full  height  of  the  photograph. 
Ihe  luiuen  of  the  ^land  is  large,  the  glands  being  hardened  in  the  distended 
condition.  The  epii  helium  lining  is  seen  to  include  a  very  large  number  of 
roundish,  clear,  and  but  slightly  staining  cells,  these  being  goblet  cells. 
The  nucleated  cells  of  the  sub-epithelial  reticular  tissue  are  seen  between  the 
glands. 


of  the  reticulum  of  the  villi,  and  from  here  into 
the  central  chyle  vessels.  The  plasma-corpuscles 
in  the  reticulum  of  the  matrix  may,  and  sometimes 
do,  take  up  chyle  globules  :  but  it  is  a  mistake  to 
ascribe    to    these    lymph  cells   an   important   role   in 


Small  and  Large  Intestixe. 


3^5 


passing  chyle  gloljules  from  the  epitheliuin   into  the 
central  chyle  vessel  (Fig.  214). 

Owing  to  the  peripheral  disposition  of  the 
capillaries  in  the  villi,  and  owing  to  the  greater 
tilling  with  blood  of  the  capillaries  during  digestion, 


.p  ^^ 


^. 


■.ch 


.^ 


i.i 


r-/..''/t?'*» 


^r 


N  '^. 


#M^ 


r**** 


Fig.  212. — From  a  Horizontal  Section  through  the  Mucous  Membrane  of 
Large  Intestine  of  Pig,  showing  the  gland  tubes  of  Lieberkiihn  in 
cross-section,  their  lining  columnar  epitlielium  with  numerous  goblet 
cells  amongst  them.  Between  the  gland  is  the  tissue  of  the  mucosa. 
(Photo.     Moderately  magnified.) 


the  villi  are  thrown  into  a  state  of  turgescence  during 
this  period,  in  consequence  of  which  the  central  chyle 
vessels  are  kept  distended.  Absorption  is  thus 
greatly  supported.  The  contraction  of  the  muscular 
tissue  of  the  villi  and  of  the  muscular  coat  of  the  in- 
testine greatly  facilitates  the  absorption  and  discharge 
of  the  chyle. 


326  Elemenis  of  Histology. 

275.  The  non-medullated  nerves  form  a  rich 
plexus,  called  the  i^lexus  myentericus  of  Auerhach 
(Fig.  215),  with  groups  of  ganglion  cells  in  the 
nodes ;  this  plexus  lies  between  the  longitudinal  and 
circular  muscular  coat.      Another  plexus    connected 


%% 


Fig.  213. — Transverse  Section  through  the  Human  A]ipendix  Verniiforiuis  ; 
showing  the  mucous  membrane  with  the  densely  arranged  glands  of 
I.ieberkiilin,  the  subuiucous  layer  with  the  cross-cut  large  vessels,  and 
the  outer  muscular  coat  covered  by  the  peritoneal  layer.  {Photo. 
Low  poicer.) 


with  the  former  lies  in  the  submucous  tissue  ;  this 
is  the  plexus  of  Meissner,  with  ganglia.  (Fig.  172.) 
In  both  plexnses  the  branches  are  of  a  very  variable 
thickness  ;  they  are  groups  of  simple  axis  cylinders, 
held  together  by  a  delicate  endothelial  sheath. 


Small  and  Large  Intestine. 


3^7 


Fig.  214.— Part  of  a  Villus  filled  with  Chyle,  from  the  intestine  of  a  puppy- 
four  days  old.     (ReidenJui.in.) 

rt,  Epithelium  of  surface  of  villus;  b,  tissue  filled  with  chyle  globules. 


rMmmM^ 


^... 


Fig,  215. — Plexus  Myentericus  of  Auerbaeh  of  the  small  intestine  of  a 
newly-born  child.     (Atlas.) 

The  minute  circles  and  ovals  indicate  sranglion  cells. 


.28 


CHAPTER   XXVITI. 

THE    GLANDS    OF    BRUNNER    AND    THE    PANCREAS. 

276.   At  the  passage  of  the    pyloric    end    of  the 
stomach  into  the  diiodeniini  (Figs.  'JOS,  216),  and  in  the 


P.G. 


<^-  ;;-sO^U^T,f^ 


MM. 


M.C. 

Fig.  216.— Section  througli  the  Gastro-duodeiialJunction.  (Microphotograph.) 

A  bandisseen  runninf,'  across  from  m.m.  to  m.m.,  the  muscularis  mucosa?.  In 
tlie  suljimicoiis  coat  beneath  on  the  right  side  are  seenBrunuers  glands, 
B.G.  In  the  mucous  coat  pyloric  ghands  are  seen  on  left  side,  p.g.  ;  villi,  v., 
and  crypts  of  Lieberkuhn,  c.l.,  on  right  side.  A  small  piece  of  muscular  coat 
is  seen  at  Ji.c. 


Glands  of  Brunwkk. 


329 


first  part  of  tlie  latter,  is  a  continuous  layer  of  gland 
tissue  in  the  submucosa,  composed  of  convoluted,  more 
or  less  branched  tubes  grouped  into  lobules,  and 
permeated  by  bundles  of  non-striped  muscular  tissue. 


^» 


M 


fti»^ 


Fig.  217. — Section  tlirougli  Pancreas  of  Cat.     {Micropliotogrwph.) 

Three  lobules  are  cut  across.  In  the  middle  of  the  small  lobule  on  the  right  a 
lighter  patch  is  seen;  this  is  an  interlobular  clump.  Similar  clumps  are 
seen  on  the  other  lobules. 


outrunners  of  the  muscularis  mucosae.  These  are  the 
glands  of  Brunner.  Numerous  thin  ducts  lined  with 
a  single  layer  of  columnar  epithelial  cells  pass  through 
the  mucosa  and  open  with  the  crypts  of  Lieberkiihn 
between  the  bases  of  the  villi.  The  gland  tubes  of 
Brunner's  glands  are  identical  in  structure  tvith  the 
pyloric  glands,  with  ichich  they  form  a  direct  ana- 
tomical continuity. 


35^ 


Elements  of  Histology. 


111.  The  pancreas  (Fig.  217)  is  in  most  respects 
identical  in  structure  with  a  serous  or  true  salivary 
gland.  The  distribution  of  the  blood-vessels  and 
lymphatics,  and  the  arrangement  of  the  connective 
tissue,  so  as  to  separate  the  ghmd  tissue  in  lobes  and 
lobules,  with  the  corresponding  inter-  and  intra-lobular 


Fig.  218. — From  a  Section  through  Pancreas  of  Dog.     {Atlas.') 

a.  Alveoli  (tuhes)  of  the  gland;  the  liuin?  cells  show  an  outer  homogeneous 
and  an  inner  granular-looking  portion  ;  d,  minute  duct. 

ducts,  are  simihxr  in  both  cases.  The  epithelium  lining 
the  latter  ducts  is  only  faintly  striated,  not  by  any 
means  so  distinctly  as  in  the  salivary  tubes.  The 
alveoli  or  acini  are  much  more  elongated  than  is  the 
case  in  the  serous  salivary  glands,  and  in  section  the 
tubular  character  of  the  alveoli  is  marked  (Fig.  218). 
The  intermediate  part  of  the  duct  leading  to  the 
alveolus  resembles  the  ductule  of  the  salivary  gland. 
The  cells  of  the  alveolus  are  somewhat  pyramidal,  and 
show  in  specimens  hardened  by  ordinar}^  reagents  an 
outer  more  deeply  staining   zone   varying   in   width. 


Pancreas. 


331 


and  an  inner  less  deeply  staining  area  (Fig.  218). 
Tiiis  lighter  zone  represents  the  part  of  the  cell  in 
which  tlie  secretory  grannies  are  collected  (Fig. 
219).       The    outer    more    deeply  staining    zone    may 


Fig.  219.— Section  througli  Pancreas.     { Micro-photograph  of  specimen 
hardened  in  osrnic  acid.) 

Several  alveoli  are  seen,  the  darker  masses  in  the  centre  of  each  being  accumu- 
lations of  secretory  granules. 


sometimes  show  a  radial  striation.  In  some  animals 
the  cells  lining  the  ductule  appear  to  be  continued  as 
an  internal  lining  into  the  alveolus.  These  constitute 
the  so-called  centro-acinous  cells  of  Lancjerhans. 
There  are  also  to  be  seen  in  the  pancreas  of  most 
animals  masses  of  cells  possessing  no  alveolar  arrange- 
ment,   staining    less    deepl}"",    but    having    large   oval 


2>2>^ 


Elements  of  Histology. 


nuclei,    which   masses   lie   here   and    there    between 
the   alveoli.       These    groups    of   cells    are    very  well 


":^..  '^L.-  ^ 


Fig.  220. — Seetior.  through  the  Pancreas  of  Cat.     (Micropliotograph.) 

In  the  central  lobule  is  seen  a  large,  slightly-stained  mass,  which  is  an  inter- 

tiihiilar  clump. 


supplied  witli  blood-vessels,  and  are  spoken  of  as 
intertiihii.lar  chimjj.'i,  or  iiiteralveolar  cell  islets  (see 
Fig.  220). 


333 


CHAPTER    XXIX. 


THE     LIVER. 


/ 


278.  The  outer  surface  of  the  liver  is  covered  with 
a   delicate   serous  membrane,,  the   peritoneum,  which, 
like  that  of  other  abdominal  organs,  has  on  its   free 
surface  a  layer  of 
endothelium.       It 
consists  chiefly  of 
fibrous  connective 
tissue. 

At  the  liilum 
or  porta  hepatis 
this  connective 
tissue  is  continued 
into  the  interior, 
where  it  joins  the 
connective  tissue 
of  the  GJisson's 
ccqysuh,  or  the  in- 
terlobular connec- 
tive tissue  (con- 
nective tissue  of 
the  portal  canals). 
This  tissue  is 
fibrous,  and  more 
or  less  lamellated  ; 
by  it  the  substance 

of  the  liver  is  subdivided  into  numerous,  more  or  less 
polyhedral,  solid  lobules  or  acini  (Fig.  221),  each 
about   2V  of  than  inch  in  diameter.      According   to 


-A 


^s 


Fig.  221.— From  a  Section  through  the  Liver  of 
Pig.  Five  lobules  are  shown.  "  They  are  well 
separated  from  one  another  by  the  inter- 
lobular tissue.     {Atlas.) 

.*,  Interlobular  connective  tissue,  containing  the 
interlobular  blood-vessels,  i.e.,  the  branches  of 
the  hepatic  artery  and  portal  vein. and  the  inter- 
lobular bile  ducts ;  i,  intralobular  or  central 
vein. 


334 


Elements  of  Histology 


whether  the  interloltular  tissue  forms  complete 
boundaries  or  not,  the  acini  appear  well  defined  from 
one  another  (pig,  ice-bear),  or  more  or  less  fused  (man 
and  carnivorous  animals  and  rodents). 

AVithin    each    acinus    there    is    only   very   scanty 
connective  tissue,  in  the  shape  of  extremely  delicate 


Fig.  222.— From  a  Vertical  Section  through  the  Liver  of  Rabbit ;  the  blood- 
vessels and  bile-vessels  injected.     i^Atlo.s.) 

a.  Interlobular  veins  sun-ounded  by  interlobular  bile  ducts  ;  these  latter  take 
up  the  network  of  fine  intralobular  bile  capillaries  ;  the  mesbes  of  this  net- 
work correspond  to  the  liver  cells  ;  h,  Intraloliular  or  central  vein. 


bundles  and  flattened  connective-tissue  cells.  Occa- 
sionally, esjDecially  in  the  young  li\'er,  lymph  cells  are 
to  be  met  with  in  the  acini  and  in  the  tissue  between 
them. 

279.  The  vena  portie  having  entered  the  hilum 
gives  off'  rapidly  numerous  branches,  which  follow  the 
interlobular  tissue  in  which  they  are  situated,  and 
they  form  rich  flexuses  around  each  ac.invs  :  these 
are    the    interlohdar    veins   (Fig.    222).       Xumerous 


LlVEK. 


335 


large 


capillary  blood-vessels  are  derived  from  these  veins. 
These  capillaries  pass  in  a  radiating  direction  to  the 
centre  of  tlie  acinus,  at  the  same  time  anastomosing 
with  one  another  by  numerous  transverse  branches. 
In  the  centre  of  the  acinus  the  capillaries  become 
confluent    into    one 


vein,  the  cen- 
tral or  intralohular 
vein.  The  intralo- 
bular veins  of  se- 
veral neighbouring 
acini  join  so  as  to 
form  t\iQ  sublohular 
veins,  andthe-e  lead 
into  the  efterent 
veins  of  the  liver, 
or  the  hepatic  veins, 
which  finally  pass 
into  the  vena  cava 
inferior. 

280.  The  sub- 
stance of  each  acinus 
—  i.e.     the     tissue 


Fig.  223. — From  a  Lobule  of  the  Liver  of 
Rabbit,  in  Avhicli  blood- and  bile-vessels  had 
been  injected,  more  highlv  magnified  than 
in  Fig.  222.     (Atlas.) 

b,  Bile  capillaries  between  the  liver  cells,  which 
are  well  shown  as  nucleated  polj'gonal  cells, 
each  with  a  distinct  reticulum  ;  c,  capillary 
blood-vessels. 


between  the  capillary  blood-vessels — is  composed  of 
uniform  polygonal  protoplasmic  epithelial  cells,  of 
about  jQ^j-yth  of  an  inch  in  diameter  ;  these  are  the 
liver  cells.  Owing  to  the  peculiar,  more  or  less 
radiating,  arrangement  of  the  capillaries,  the  liver 
cells  appear  to  form  columns  or  cylinders,  also  more 
or  less  radiating  from  the  periphery  towards  the  centre 
of  the  acinus.  The  cells  contain  particles  of  glycogen 
in  various  amounts.  According  to  Brunton  and 
Delepine,  the  amount  gradually  increases  in  the 
rabbit's  liver  after  a  meal,  and  reaches  its  maximum 
between  the  third  and  eighth  hour.  They  also  contain 
pigment  granules,  which,  being  derived  from  the 
disintegration  of   haemoglobin  in  the  spleen,  include 


336  Elements  of  Histology. 

iron.  Each  liver  cell  shows  a  more  or  less  fibrillateJ 
protoplasm  (Kupfer),  and  in  the  centre  a  spherical 
nucleus  with  one  or  more  nucleoli. 

The  liver  cells  are  joined  by  an  albuminous  cement 
substance,  in  which  are  left  fine  channels  ;  these  are  the 
hile  capillaries  (Figs.  223  and  2'2-i).  In  a  successfully 
injected  preparation  the  liver  cells  appear  separated 
everywhere  from  one  another  by  a  bile  capillary,  and 
these  form  for  lite  ivhole  acinus  a  continuous  inter- 
cominunicating  network  of  minute  channels.  Where 
the  liver  cells  are  in  contact  with  a  capillary  blood- 
vessel, there  are  no  bile  capillaries. 

281.  At  the  margin  of  the  acinus  the  bile  capil- 
laries are  connected  with  the  lumen  of  minute  tubes  ; 
these  jDOssess  a  membrana  propria  and  a  lumen  lined 
with  a  single  layer  of  transparent  polyhedral  epithelial 
cells.  These  are  the  small  interlobular  hile  ducts 
(Fig.  222).  Their  epithelial  cells  are  in  reality 
continuous  with  the  liver  cells.  These  ducts  join 
and  form  larger  interlobular  hile  ducts,  lined  with 
more  or  less  columnar  epithelium.  The  first  part  of 
the  bile  duct  lined  with  polyhedral  cells  corresponds 
to  the  intermediary  part  of  the  ducts  of  the  salivary 
glands.  The  interlobular  bile  ducts  form  networks 
in  the  interlobular  tissue.  Towards  the  hilum  they 
become  of  great  diameter,  and  their  wall  is  made  up 
of  fibrous  tissue,  and  in  it  are  bundles  of  non-striped 
muscular  cells.  Small  mucus-secreting  glands  are  in 
their  wall,  and  open  into  their  lumen. 

The  wall  of  the  hepatic  duct,  and  of  the  gall 
bladder,  are  merely  exaggerations  of  a  large  bile  duct. 

282.  The  hepatic  artery  follows  in  its  ramification 
the  interlobular  veins.  The  arterial  branches  form 
plexuses  in  the  interlobular  tissue,  and  they  supply 
the  capillary  blood-vessels  of  the  interlobular  connective 
tissue,  and  especially  of  the  bile  ducts.  The  capillary 
blood-vessels  of   the  bile  ducts  join    so    as    to    form 


Liver. 


337 


small  veins,  wliicli  finally  empty  themselves  into 
the  hepatic  veins.  The  anastomoses  between  the 
capillary  blood  -  vessels,  derived  from  the  arterial 
branches,  and  the  capillary  blood-vessels  of  the  acini, 


Fig.  224.— From  a  Section  tlirougli  the  Liver  of  Rabbit,  of  which  the  bile 
ducts  had  been  injected  ;  showing  the  distribution  of  the  bile  capillaries 
and  their  branchlets  between  the  liver  cells.  (Fhotograpli.  Moderately 
magnified.) 

are  insignificant  (Cohnheim  and  Litten).  The  serous 
covering  of  the  liver  contains  special  arterial  branches 
—  rami  capsulares.  Networks  of  lymphatics — deep 
lymphatics — are  present  in  the  interlobular  connective 
tissue,  forming  plexuses  around  the  interlobular  blood- 
vessels and  bile  ducts,  and  occasionally  forming  a 
perivascular  lymphatic  around  a  branch  of  the  hepatic 
vein.  Within  the  acinus,  the  lymphatics  are  repre- 
w 


^T,S  Elements  of  Histology. 

sented  only  by  spaces  and  clefts  existing  between  the 
liver  cells  and  capillary  blood-vessels ;  these  are  the 
intralohidar  lymphatics  (Macgillivray,  Frey,  and 
others).  They  anastomose  at  the  margin  of  the 
acinus  with  the  interlobular  lymphatics. 

In  the  capsule  of  the  liver  is  a  special  network 
of  lymphatics  called  the  superficial  lyinphatics. 
Numerous  branches  pass  between  this  network  and 
the  interlobular  lymphatics. 


539 


CHAPTER  XXX. 

THE    ORGANS    OF    RESPIRATION. 

283.  I.  The  larynx — The  supporting  frame- 
work of  the  larynx  is  formed  by  cartilage.  In  the 
epiglottis  the  cartilage  is  elastic  and  reticulated — i.e. 
the  cartilage  plate  is  perforated  by  numerous  smaller 
and  larger  holes.  The  cartilages  of  Santorini  and 
Wrisbergii,  the  former  attached  to  the  top  of  the 
arytenoid  cartilage,  the  latter  enclosed  in  the  aryteno- 
epiglottic  fold,  are  also  elastic.  The  thyroid,  cricoid, 
and  arytenoid  cartilages  are  hyaline.  All  these  are 
covered  with  the  usual  perichondrium. 

A  small  no  lule  of  elastic  cartilage  is  enclosed  in 
the  front  part  of  the  true  vocal  cord.  This  is  the 
cartilao^e  of  Luschka. 

The  mucous  membrane  lining  the  cavity  of  the 
larynx  (Fig.  225)  has  the  following  structure  : — 

The  internal  or  free  surface  is  covered  with 
ciliated  stratified  columnar  epithelium  :  the  most 
superficial  cells  are  conical  cells  with  cilia  on  their 
free  surface  ;  then  between  the  extremities  of  these 
cells  are  wedged  in  spindle-shaped  and  inverted 
conical  cells.  Numerous  goblet  cells  are  found 
amongst  the  superficial  cells.  The  two  surfaces  of 
the  epiglottis  and  the  true  vocal  cords  are  covered 
with  stratified  pavement  epilheli^im. 

Underneath  the  epithelium  is  a  basement  mem- 
brane separating  the  former  from  the  mucous  mem- 
brane proper. 

284.  Themucojs  membrane  is  delicate  connective 


;4C 


Elements  of  Histology. 


tissue  with  numerous  lymph  corpuscles.  In  the  pos- 
terior surface  of  the  epiglottis,  in  the  false  vocal  cords, 
and   especially   in  the  ventricle  of  the    larynx,   this 


7n  — 


\  ^^^  >-  ^  ^ 

In  ^-S2>  ^^*'.\ 


„H(^ 


Fig.  225.— From  a  Longitudinal  Section  through  the  Ventricle  of  the  Larvnx 
of  a  Child.     (Atlas.) 

a,  True  vocal  cord ;  b,  false  vocal  cord  ;  c.  nodule  of  elastic  cartilage  (cartilage 
of  Luschka):  d,  ventricle;  I,  lymphatic  tissue  ;  m,  bundles  of  the  thyro- 
arytenoid muscle  in  transverse  section. 

infiltration  amounts  to  diffuse  adenoid  tissue,  and 
even  to  the  localisation  of  this  as  lymph  follicles. 
In  both  surfaces  of  the  ej^iglottis,  and  in  the  true 
vocal  cords,  the  mucosa  extends  into  the  stratified 
pavement  epithelium  in  the  shape  of  minute  papillae. 

In  the  lower  part  of  the  larynx  the  mucous  mem- 
brane contains  bundles  of  elastic  fibres  connected  into 


Larvnx.\ 


341 


networks,  antl  running  in  a  longitudinal  direction. 
Those  elastic  fibres  are  found  chieHy  in  the  superficial 
parts  of  the  mucous  membrane.      Tn  the  true   vocal 


X  40.     {Photograph  by  Mr 


Fig.  226. — Section  through  Trachea  of  Foitus. 

A.  Pringle.) 

1,  Ciliated  columnar  epithelium  of  internal  surface;  2,  mucous  membrane  with 
its  glands  ;  ?,,  cartilage ;  4,  outside  this  the  thyroid  gland. 


cords  the  mucosa  is  entirely  made  up  of  elastic  fibres 
extending  in  the  direction  of  the  vocal  cords. 

285.  The  deeper  part  of  the  mucous  membrane  is 
of  loose  texture,  and  corresponds  to  the  submucosa  ; 
in  it  are  embedded  numerous  mucous  glands,  the 
ducts  of  which  pass  through  the  mucosa  and  open  on 
the  free  surface.  The  alveoli  of  the  glands  are  of  the 
nature  of  mucous  alveoli — i.e.  a  considerable  lumen 
lined  with  a  layer  of  mucous  goblet  cells.     There  are, 


342 


Elements  of  Histologw 


however,  also  alveoli  lined  with  columnar  albuminous 
cells,  and  such  as  have  Ijoth  side  by  side,  as  is  the  case 


i^t^-^'iVmrr/r-^i^'-r-i-'. 


g»y'.;?j7-^[7f^| 


m 


•^ 


wn 


V. 


iV^ 


^^ 


I 


Fig.   227.— From  a  Longitudinal  Section  tlirougli  the  Trachea  of  a  Child. 

{Atlas.) 

a.  Stratified  columnar  ciliated  epitheMum  of  the  internal  free  surface:  ft,  base- 
ment nienihrane ;  c,  mucosa  ;  d.  networks  of  longitudinal  elastic  tihres  ;  the 
oval  nuclei  bL-tween  them  indicate  connective-tissue  corpuscles;  e,  sub- 
mucous tissue  containing  mucous  glands;  /,  large  blood-vessels;  g,  fat 
cells  ;  h,  hyaline  cartilage  of  the  tracheal  rings. 

in  the  sublingual  dand  of  the  dof?.  The  ciliated 
epithelium  of  the  surface  in  some  places  extends  also 
for  a  short  distance  into  the  ducts.  The  true  vocal 
cords  have  no  mucous  glands. 

The  Ijlood-vessels  terminate  with  the  capillary  net- 


Trachea.  343 

work  in  the  superficial — i.e.  &u)>epithelial — layer  of 
the  mucosa ;  where  tliersj  are  papilla; — i.e.  in  the 
epiglottis  and  true  vocal  cords — these  receive  a  loop 
of  capillary  blood-vessels.  The  lymphatics  form  super- 
ficial networks  of  fine  vessels  and  deep  submucous 
networks  of  large  vessels.  These  are  of  enormous 
width  and  size  in  the  membrane  of  the  anterior  surface 
of  the  epiglottis.  The  finer  nerves  form  superficial 
plexuses  of  non-medullated  fibres,  some  of  which  ter- 
minate, according  to  Luschka  and  Boldyrew,  as  end 
bulbs.  Taste  buds  have  been  found  in  the  epithelium 
of  the  posterior  surface  of  the  epiglottis  (V(  rson, 
Schofield,  Davis),  and  also  in  that  of  the  deeper  parts 
of  the  larynx  (Davis). 

286.  II.  The  trachea — The  trachea  is  very 
similar  in  structure  to  the  lower  part  of  the  larynx, 
from  which  it  differs  merely  in  possessing  the  rings 
of  hyaline  cartilage,  and  in  containing,  in  the  posterior 
or  membranous  portion,  transverse  bundles  of  non- 
strijoed  mnscrdar  tissue,  extending  horizontally  between 
the  ends  of  the  rings.  Its  com])onent  parts  are  (Figs. 
226,227,  228):— 

{a)  a  stratified  columnar  ciliated  epithelium  ; 

{Jj)  a  basement  membrane  ; 

(c)  a  mucosa,  with  the  terminal  networks  of  capil- 
lary blood-vessels,  and  infiltrated  with  adenoid  tissue  ; 

{d)  a  layer  of  longitudinal  elastic  fibres  connected 
into  networks  ; 

(e)  a  loosely  textured  submucous  tissue,  contain- 
ing the  large  vessels  and  nerves  and  small  mucous 
glands.  Occasionally  the  gland  or  its  duct  is  em- 
bedded in  a  lymph  follicle. 

287.  III.    The    bronchi    and    the    lung: 

The  bronchi  ramify  within  the  lung  dendritically 
into  finer  and  finer  tubes.  The  finest  branches  are 
the  terminal  bronchi.  In  the  bronchi  we  find,  instead 
of  rings  of  hyaline  cartilage,  as  in  the  trachea,  larger 


344 


Elements  of  Histology. 


and  smaller  oblong  or  irregularly-sliaped  plates  of 
hyaline  cartilage  distributed  more  or  less  uniformly 
in  the  circumference  of  the  wall.  Towards  the  small 
microscopic  bronchi  these  cartilage  plates  gradually 
diminish  in  size  and  number.      The  epithelium,   the 


Fig.  228.— From  a  Section  througli  the  Traclieal  Mucous  Membrane  of  a 
Newly -born  Child.     {Photo.     Highly  magnified.) 

e.  Ciliated  columnar  epithelium  ;  amongst    the    ciliated  cells  are   numerous 
goblet  cells  ;  m,  mucosa  ;  </,  acini  of  mucous  glands. 

basement  membrane,  the  sub-epithelial  mucosa,  and 
the  layer  of  longitudinal  elastic  fibres,  remain  the 
same  as  in  the  trachea.  The  submucous  tissue  con- 
tains small  mucous  glands. 

288.  Between  the  sub-epithelial  mucosa  and  the 
submucosa  is  a  continuous  layer  of  circidar  non- 
striped  muscular  tissue.     In  the  smaller  microscopic 


Bronchi  and  Lung.  345 

bronchi  this  layer  is  one  of  the  most  conspicuous.  By 
the  contraction  of  tlie  circuhir  muscular  coat  the 
mucosa  is  placed  in  longitucliiuil  folds. 

The  state  of  contraction  and  distension  of  the 
small  bronchi  bears  an  important  relation  to  the  aspect 
of  the  epitheliuui,  wliich  appears  as  a  single  layer  of 
columnar  cells  in  the  distended  bronchus,  and  as 
stratified  when  the  bronchus  is  contracted. 

The  distribution  of  the  blood-vessels  is  the  same 
as  in  the  trachea.  Lymph  follicles  are  met  with  in 
the  submucous  tissue  of  the  bronchial  wall  in  animals 
and  man. 

The  lymphatic  networks  of  the  bronchial  mucous 
membrane  are  very  conspicuous.  Those  of  the  sub- 
mucous tissue — i.e.  the  peribronchial  lyniphatics — 
anastomose  with  those  surrounding  the  pulmonary 
blood-vessels. 

Pigment  and  small  particles  can  be  easily  absorbed 
through  the  cement  substance  of  the  epithelium  into 
the  radicles  of  the  superficial  lymphatics,  whence  they 
pass  readily  into  the  (larger)  peribronchial  lymphatics. 

In  connection  with  the  nerve  branches  in  the 
bronchial  wall  are  minute  ganglia. 

289.  Each  terminal  bronchiole  branches  into 
several  wider  tubes  called  the  alveolar  ducts.,  or 
infundibula  ;  each  of  these  branches  again  into  several 
similar  ducts.  All  ducts,  or  infundibula,  are  closely 
beset  in  their  whole  extent  with  spherical,  or,  being 
pressed  against  one  another,  with  polygonal  vesicles — - 
the  air  cells  or  cdveoli — opening  by  a  wide  aperture 
into  the  alveolar  duct  or  infundibulum,  but  not  com- 
municating with  each  other.  The  infundibula  are 
much  wider  than  the  terminal  bronchioles,  and  also 
wider  than  the  alveoli. 

290.  All  infundibula  with  their  air  cells,  belonging 
to  one  terminal  bronchiole,  represent  a  conical  struc- 
ture, the  apex  of  which   is  formed  by  the  terminal 


346 


Elements  of  Histology. 


bronchus.  Such  a  conical  mass  is  a  lobule  of  the 
lung,  and  the  whole  tissue  of  the  lung  is  made  up  of 
such  lobules  closely  aggregated,  and  arranged  as  lobes. 
The  lobules  are  separated  from  one  another  by  deli- 
cate fibrous  connective  tissue  :  this  forms  a  continuity 


Fig.  229. — From  a  Section  through  the  Lung  of  Cat,  stained  with  nitrate  of 
silver.     {Atlas.) 

a,  Infun(iil>ulum  or  alveolar  duct  in  cross-section  ;  b.  groups  of  polyhedral 
cells  lining  one  part  of  the  infundibulum,  the  rest  being  lined  with  fliittened 
transparent  epithelial  scales ;  c,  alveoli  lined  with  flattened  epithelial 
scales  ;  here  and  there  between  them  is  seen  a  polyhedral  trranular  epithelial 
cell. 

with  the  coDiieetive  tissue  accompanying  the  bronchial 
tubes  and  large  vascular  trunks,  and  with  these  is 
traceable  to  the  hilum.  On  the  other  hand,  the  inter- 
lobular connective  tissue  of  the  superficial  parts  of  the 
lung   is  continuous    with    the    fibrous    tissue    of    the 


Brlwchi  axd  Lung.  347 

surface  called  the  pleura  pulmonalis.  This  membrane 
contains  numerous  elastic  libres,  and  on  the  free 
surface  is  covered  with  a  hiyer  of  endothelium. 

In  some  instances  (guinea-pig)  the  pleura  pulmo- 
nalis contains  bundles  of  non-striped  muscular  tissue. 

The  lobes  of  the  lung  are  separated  from  one 
another  by  large  septa  of  connective  tissue— the  liga- 
menta  pulmonis. 

291.  The  teriiiiiial  bronchi  contain  no  cartilage 
or  mucous  fflands  in  their  wall.  This  is  made  up  of 
three  coats  :  («)  a  delicate  epithelium — a  single  layer 
of  small  jxjhjhedral  (jranular-Jooking  cells ;  (h)  a 
circular  coat  of  non-striped  muscular  tissue ;  and  (c) 
a  tine  ad\entitia  of  elastic  fibres,  arranged  chiefly  as 
longitudinal  networks. 

292.  Tracing  the  elements  constituting  the  wall 
of  a  terminal  bronchiole  into  the  infundibula  and  air 
cells  (Fig.  229)  we  find  the  following  changes  :  {«)  the 
polyhedral  granular-looking  epithelial  cells  forming 
a  continuous  lining  in  the  terminal  bronchiole  are 
traceable  into  the  infundibulum  only  as  larger  or 
smaller  groups  :  between  these  groups  of  small  poly- 
hedral granular-looking  cells  large,  flat,  transparent, 
homogeneous,  nucleated,  epithelial  scales  make  their 
appearance.  The  farther  away  from  the  terminal 
bronchiole,  the  fewer  are  the  groups  of  polyhedral 
granular-lookinf;  cells.  In  all  infundibula.  however, 
the  transparent  scales  form  the  chief  lining.  This 
becomes  still  rnoie  marked  in  the  air  cells.  There  the 
small  polyhedral  granular-looking  cells  are  traceable 
only  singly,  or  in  groups  of  two  or  three  (Elens),  the 
rest  of  the  cavity  of  the  fir  cells  being  lined  with  the 
large  transparent  scales. 

In  the  foetal  state  all  cells  lining  the  infundibula 
and  air  cells  are  of  the  small  polyhedral  granular- 
looking  variety  (Kuttner).  With  the  expansion  of 
the  lungs  during  the  first  inspiration  many  of  these 


348 


Elements  of  Histology. 


cells  change  into  the  large  transparent  scales,  in  order 
to  make  up  for  the  increment  of  surface.  A  lung 
expanded  ad  maximum  shows  much  fewer  or  none  of 
the  small  polyhedral  cells  ;  while  a  lung  that  is  col- 
lapsed shows  them  in  groups  in  the  infundiljula,  and 
isolated  or  in  twos  or  threes  in  the  alveoli. 


Fig.  230.— Network  of  Capillary  Blood-vessels  surrounding  the  Alveoli  of 
the  Human  Lung.     (Photograph  by  Mr.  A.  Pringle.) 


293.  (b)  The  circular  coat  of  non-striped  muscular 
tissue  of  the  terminal  bronchiole  passes  as  a  continuous 
circular  coat — but  slightly  thinner — on  to  the  alveolar 
ducts  or  infundibula,  in  their  whole  extent,  but  not 
beyond  them,  i.e.  not  on  to  the  air  cells. 

(c)  The  adventitia  of  elastic  networks  is  continued 
on  the  infundibula,  and  thence  on  the  air  cells,  where 


Bronchi  and  Lung.  349 

it  forms  an  essential  part  of  the  wall  of  the  alveoli, 
being  its  framework. 

Amongst  the  network  of  elastic  fibres  forming  the 
wall  of  the  alveoli  is  a  network  of  branched  connec- 
tive-tissue cells,  contained  as  usual  in  similarly-shaped 
branched  lacun?e,  which  are  the  radicles  of  the  lym- 
phatic vessels. 

294.  The  blood-vessels  and  lyiiipliatics. — 
The  branches  of  the  pulmonary  artery  and  veins  are 
contained  within  the  connective  tissue  separating  the 
lobes  and  lobules,  whence  they  can  be  traced  into 
their  finer  ramifications  towards  the  infundibula  and 
air  cells.  Each  of  these  latter  is  surrounded  by  a  sort 
of  basket-shaped  dense  network  of  capillary  blood- 
vessels (Figs.  230  and  231).  The  capillary  networks 
of  adjacent  alveoli  are  continuous  with  one  another, 
and  stand  in  communication  on  the  one  hand  with  a 
branch  of  the  pulmonary  artery,  and  on  the  other  with 
branches  of  the  pulmonary  vein.  The  branches  of 
the  bronchial  artery  belong  to  the  bronchial  walls, 
which  are  supplied  by  them  with  capillary  networks. 

The  lacunse  and  canaliculi  in  the  wall  of  the 
alveoli,  mentioned  above,  are  the  rootlets  of  lymphatic 
vessels,  which  accompany  the  pulmonary  vessels,  and 
form  a  network  around  them ;  these  are  the  deep 
lymphatics,  or  the  "perivascular  lympJtatics.  They  are 
connected  also  with  the  networks  of  lymphatics  sur- 
rounding the  bronchi,  i.e.  the  peribronchial  lymphatics. 
The  rootlets  of  the  superficial  air  cells  empty  them- 
selves into  the  siib-j)leural  j^le.mis  oflymj^hatics.,  a  rich 
plexus  of  large  lymphatics  with  valves.  All  these 
lymphatics  lead  by  large  trunks  into  the  bronchial 
lymph  glands. 

295.  Between  the  flattened  transparent  epithelial 
cells  lining  the  alveoli  are  minute  openings,  stomata 
(Fig.  229),  leading  from  the  cavity  of  the  air  cells  into 
the  lymph  lacunae  of  the  alveolar  wfiU.     These  stomata. 


350 


Elements  of  Histology. 


are  more  distinct  during  expansion,  i.e.  inspiration, 
than  in  the  collapsed  state.  Inspiration,  by  its  ex- 
panding the  lungs,  and  consequently  also  the  lym- 
phatics, greatly  favours  absorption.  Through  these 
stomata,    and    also   throuirh    the    interstitial    cement 


Fig.  231.— Injected  Lung  of  Cat.     (Photograph.) 


substance  of  the  lining  epithelium,  formed  particles 
— such  as  soot  particles  of  a  smoky  atmosphere, 
pigment  artificially  inhaled,  cellular  elements,  such 
as  mucous  or  pus  corpuscles,  bacteria,  etc. — find  their 
way  into  the  radicles  of  the  lymphatics,  thence  into 
the  perivascular  and  sub-pleural  lymphatics,  and  finally 
into  the  bronchial  glands. 

The  cellular  elements  just  mentioned,  containing 
particles  of  soot,  are  spoken  of  as  "  dust  cells." 


.53 


CHAPTER   XXXI. 


THE    SPLEEX. 


296.  The  capsule   enveloping   the    spleen    is  a 
serous  membrane — the  peritoneum.      It  is  a  connec- 


c     i 

0*  '0  , 


Tig.  232.— From  a  Vertical  Section  through  the  Spleen  of  Ape.     (Atlas.) 

a.  Capsule;  b,  rrabeculEe;  c.  Malpighian  corpuscle:  d,  artery  ensheathed  in  a 

Malpit'hian  corpuscle  ;  e,  pulp  tissue. 

tive-tissue  membrane  with  networks  of  elastic  fibres, 
and  covered  on  its  free  surface  with  an  endothelium. 


v5D- 


Elemexts  of  Histology. 


The  deep  part  of  the  capsule  contains  bundles  of  non- 
striped  miLscuIar  tissue  forming  plexuses.  In  man 
the  bundles  are  relati\ely  thin,  but  in  some  mammals 
- — e.g.  dog,  pig,  horse — they  are  continuous  masses 
arranged  sometimes  as  a  deep  longitudinal  and  a 
superficial  circular  layer  (Fig.  232). 

In  connection  with  the  capsule  are  the  trahecuhe- 
(Fig.  232).  These  are  microscopical,  thicker  or  thinner 
cylindrical  bands  branching  and  anastomosing,  and 
thus  making  a  framework  in  which  the  tissue  of 
the  spleen  is  contained.  Towards  the  hilum  the 
trabeculye  are  larger,  and  they  form  there  a  continuity 
with  the  connective  tissue  of  the  hilum.  They  are 
the  carriers  of  the  large  vascular  branches.  The 
trabecul^e  in   the    human    spleen    consist    chieflv    of 


fibrous     tissue     with    an    admixture    of    longitudinal 

non-striped  muscu- 
lar tissue.  This  is 
more  pronounced  in 
the  dog,  horse,  pig, 
guinea-pig,  in  which 
the  trabeculae  are 
chiefly  composed  of 
non-striped  muscu- 
lar tissue.  Folio  v\-- 
ingasmalltrabecula 
after  it  is  given  off 
from  a  larger  one, 
we  tind  it  branch- 
ing into  still  smaller 
ones,  winch  ulti- 
mately lose  them- 
selves amongst  the 
spleen    tissue    called 


Fig.  233.— From  a  Section  through  the  Pulip 
of  the  Spleen  of  Pig.     ( Atlas. ) 

a.  Last  outrunners  of  the  muscular  trabecule ; 
b,  flattened  cells  forming  the  honevcomhed 
matrix  of  the  pulp:  in  the  meshes  of  this 
matrix  are  contained  lymphoid  cells  of  various 
sizes. 


of   the 


elements    of    that   part 
spleen  pulp  (Fig.  233). 

Tlie  meshes  of  the  network  of  the  trabecular  are 
filled  up  with  the  parenchyma.      This  consists  of  two 


Spleex.  353 

kinds  of  tissues  :  {a)  the  Malpighian  corpuscles  ;  and 
(Jj)  the  pulp  tissue. 

297.  The  .llal|ii;:liiaii  corpuscles  are  masses 
of  adenoid  tissue  connected  with  the  branches  of  the 
splenic  artery.  Following  the  chief  arterial  trunks  as 
they  pass  in  the  big  trabeculfe  towards  the  interior 
of  the  spleen,  they  are  seen  to  give  off  numerous 
smaller  l>ranches  to  the  spleen  parenchyma  ;  these  are 
ensheathed  in  masses  of  adenoid  tissue,  which  are 
either  cylindrical  or  irregularly-shaped,  and  in  some 
places  form  oval  or  spherical  enlargements.  These 
sheaths  of  adenoid  tissue  are  traceable  to  the  end  of 
an  arterial  branch  ;  and  in  the  whole  extent  the 
adenoid  tissue  or  ^Malpighian  corpuscle  is  supplied  b}^ 
its  artery  with  a  network  of  capillary  blood-vessels. 

298.  The  rest  of  the  spleen  parenchyma  is  made  up 
of  the  pulp.  The  matrix  of  this  is  a  honeycombed, 
spongy  network  of  fibres  and  septa,  which  are  the 
processes  and  bodies  of  large,  flattened,  endotheloid 
cells,  each  with  an  oval  nucleus.  In  some,  es^^ecially 
young,  animals,  some  of  these  cells  are  huge  and 
multinucleated.  The  spaces  of  the  honeycombed  tissue 
are  of  different  diameters,  some  not  larger  than  a  blood 
corpuscle,  others  large  enough  to  hold  several.  All 
spaces  form  an  intercommunicating  system.  The 
spaces  contain  nucleated  lymph  corpuscles,  more  or 
less  connected  with  and.  derived  from  the  cell  plates 
of  the  matrix.  But  they  do  not  fill  the  spaces,  so 
that  some  room  is  left,  large  enough  to  allow  blood 
corpuscles  to  pass. 

The  spaces  of  the  honeycomljed  pulp  matrix  are  in 
communication,  on  the  one  hand,  with  the  ends  of  the 
capillary  blood-vessels  of  the  Malpighian  corpuscles, 
and,  on  the  other,  they  open  into  the  venous  radicles 
or  sinuses  (Fig.  234),  udiich  are  oblong  spaces  lined 
with  a  layer  of  more  or  less  polyhedral  endothelial  cells. 
These  sinuses  form  networks,  and  lead  into  the  large 


354 


Elements  of  Histology. 


venous  branches  passing  in  the  big  trabeculse  to  the 
hihun.      The  venous  sinuses  in  man  and  ape  possess  a 
special  adventitia  formed  of  circular  elastic  fibrils. 
Not    all     arterial     branches     are     ensbeatlied    in 


-AL 


Fig.  234. — From  a  Section  through  the  Spleen  of  a  Guinea-pig ;  the  blood- 
vessels had  been  injected.     {Atlas  ) 

a,  Artery 'of  Malpighian  corpuscle;  h.  pulp;  hetween  its  cells  are  the  minute 
blood-ctiannels  opening  into  c,  the  radicles  of  the  veins. 


Malpighian  corpuscles;  some  few  fine  arterial  branches 
open  directly  into  the  veins  of  the  pulp  matrix,  being 
invested  in  a  peculiar  reticular  or  concentrically 
arranged  cellular  tissue  (not  adenoid).  These  are  the 
capillary  sheaths  of  Schweigger  Seidel. 

299.  The    blood    passes   then    from    the    arterial 
branches  through  the  capillaries   of  the  ^Malpighian 


Spleex.  355 

corpuscles,  whence  it  travels  into  the  labyrinth  of 
minute  spaces  in  the  honeycombed  pulp  matrix ; 
thence  it  passes  into  the  venous  sinuses,  and  finally 
into  the  venous  trunks.  The  current  of  blood  on  its 
passage  through  the  pnlp  tissue  becomes,  therefore, 
greatly  retarded.  Under  these  conditions  numerous 
red  blood-corpuscles  appear  to  be  taken  up  by  the 
cells  of  the  pulp,  some  of  which  contain  several 
in  their  interior.  In  these  corpuscles  the  blood  discs 
become  gradually  broken  up,  so  that  finally,  only 
granules  and  small  clumps  of  blood  pigment  are  left 
in  them.  The  presence  of  blood  pigment  in  the 
corpuscles  of  the  pulp  is  explained  in  this  way  ;  and 
it  is  therefore  said  that  the  pulp  tissue  is  a  destroyer  of 
red  blood-corpuscles. 

The  pulp  tissue  is  most  probably  the  birthplace  of 
colourless  blood-corpuscles;  and  according  to  Bizzozero 
and  Salvioli  it  is  also  the  birthplace  of  red  blood- 
corpuscles. 

The  hjmphatics  form  plexuses  in  the  capsule 
(Tomsa,  Kyber).  These  are  continuous  with  the  plexus 
of  lymphatics  of  the  trabecul^e  :  and  these  again  with 
the  plexus  of  lymphatics  in  the  adventitia  of  the 
arterial  trunks. 

Xon-meduUated  nerve  fibres  have  been  traced  along 
the  arterial  branches. 


356 


CHAPTER    XXXII. 

THE    KIDNEY,    URETER    AXD    BLADDER. 

300.  A.     The  framework. 

The  kidney  possesses  a  thin  investing  capsule  com- 
posed of  fibrous  tissue,  more  or  less  of  a  lamellar 
arrangement.  Bundles  of  fibrous  tissue  pass  with 
blood-vessels  between  the  deeper  part  of  the  capsule 
and  the  parenchyma  of  the  periphery.  According 
to  Eberth,  a  plexus  of  non-striped  muscle  cells  is 
situated  underneath  the  capsule. 

The  ureter  entering  the  hilum  enlarges  into  the 
pelvis  of  the  kidney,  and  with  its  minor  recesses  or 
prolongations  forms  the  calices.  Both  the  pelvis  and 
the  calices  are  limited  by  a  wall  which  is  a  direct  con- 
tinuation of  the  ureter.  The  internal  free  surface  is 
lined  with  stratified  transitional  epithelium.  Under- 
neath the  epithelium  is  a  fibrous  connective- tissue 
membrane  (the  mucosa),  containing  the  networks  of 
capillary  blood-vessels  and  fine  nerve  fibres.  Outside 
the  mucosa  and  insensibly  passing  into  it  is  the 
loose-textured  submucosa,  with  groups  of  fat  cells. 
There  are  present  in  the  submucosa  bundles  of 
non-striped  muscular  tissue,  continued  from  the 
ureter,  in  the  shape  of  longitudinal  and  circular 
bundles. 

In  the  pelvis  of  the  kidney  of  the  horse  small 
alands  (simple  or  branched  tubes),  lined  with  a  single 
layer  of  columnar  epithelial  cells,  have  been  observed 
by  Paladino,  Sertoli,  and  Egli.  The  last-named 
mentions  also  that  in  the  pelvis  of  the  human  kidney 


Kidney,   Ureter  and  Bladder.  357 

there  are  gland-tubes  similar  in  structure  to  sebaceous 
follicles. 

301.  The  large  vascular  trunks  enter,  or  pass  from 
the  tissues  of  the  calices  into  the  parenchyma  of  the 
kidney  between  the  cortex  and  medulla,  and  they  are 
accompanied  by  bundles  of  fibrous  connective  tissue 
and  a  few  longitudinal  bundles  of  non-striped  muscular 
tissue,  thereby  separating  the  individual  Malpighian 
pyramids. 

The  parenchyma  itself  contains  ver}^  scanty  fibrous 
connective  tissue,  chiefly  around  the  Malpighian  cor- 
puscles and  around  the  arterial  vessels,  especially  in 
the  young  kidney.  In  the  jDapilhe  there  is  relatively 
a  great  amount  of  fil>rous  tissue.  On  the  surface  of 
the  papillae  (facing  the  calices)  there  is  a  continuous 
layer  of  tibrous  tissue,  and  this  on  its  free  surface 
is  covered  with  stratified  transitional  epithelium. 

The  parenchyma  of  the  kidney  consists  entirely  of 
the  urinary  tubules  and  the  intertubular  blood-vessels, 
and  there  is  an  interstitial  or  intertubular  connective- 
tissue  framework  in  the  shape  of  honeycombed  hyaline 
membranes  with  flattened  nucleated  branched  or 
spindle-shaped  cells.  The  meshes  of  the  honeycomb  are 
the  spaces  for  the  urinary  tubules  and  blood-vessels. 

302.  B.  The  pareiicliyma. — I.  The  urinary 
tubules  (Fig.  235). — In  a  transverse  or  longitudinal 
section  through  the  kidney  we  notice  the  cortex,  the 
houndary  layer  of  Ludwig  and  the  papillary  j)ortions, 
the  last  terminating  in  the  conical ^;«^?j<7/rti  in  the  cavity 
of  the  calices. 

The  boundary  layer  and  the  papillary  portion 
form  the  medulla.  A  papilla  with  the  papillary 
portion  and  boundary  layer,  continuous  with  it, 
constitutes  a  MalpiyJiian  pyramid.  The  medulla  of 
the  human  kidney  contains  about  a  dozen  of  such 
Malpighian  pyramids. 

303.  The     cortex     contains     vast     numbers     of 


358 


Elements  of  Histology. 


Fig.  235. — Diagram  showing  the  course  of  the  Uriniferous  Tubules  in  the 

difterent  parts  of  the  cortex  and  medulla.     {Atla&,) 

(For  description  of  this  Fig.  see  foot  of  next  page.) 


Kidney,    Uri:ti:r  and  Bladder.  359 

convoluted  tubules  with  their  c.ecal  origin  in  the 
Malpighian  corpuscles  ;  this  is  the  lahnrinth  separated 
into  numerous  divisions  of  ecjual  breadth  by  regulai-ly- 
disposed  straight  stria?  originating  a  sliort  distance 
from  the  outer  capsule,  and  ratliating  towards  the 
boundary  layer  through  which  they  pass.  Each  of 
these  stria3  is  a  bundle  of  straight  tubules,  and 
represents  a  mednUary  ray.  The  boundary  layer 
shows  a  uniform  vertical  striation,  in  which  opa(pie 
and  transparent  strife  alternate  with  one  another.  The 
opacpie  stria^  are  continuations  of  the  medullar}^  I'ays, 
the  transparent  striae  are  bundles  of  blood-vessels. 

The  papillary  portion  is  uniformly  and  vertically 
striated. 

Tracing  a  medullary  ray  from  the  boundary  layer 
into  the  cortex,  it  is  seen  that  its  breadth  gradually 
diminishes,  and  it  altogether  ceases  at  a  short  distance 
from  the  outer  capsule.  A  medullary  ray  is,  con- 
sequently, of  a  conical  shape,  its  apex  being  situated 
at  the  periphery  of  the  cortex,  its  base  in  the 
boundary  layer.  Such  a  pyramid  is  called  a  pyramid 
of  Ferrein. 

304.  All  urinary  tubules  commence  as  convoluted 
tubules  in  the  part  of  the  cortex  named  the 
labyrinth,  but  not  in  the  medullary  rays,  with  a 
Cfecal  enlargement  called  a  Malpighian  corpuscle^  and 
terminate — having  previously  joined  with  many  other 
tubules  into  larger  and  larger  ducts— at  one  of  the 
many  minute  openings  or  mouths  at  the  apex  of  a 
papilla.  On  their  way  the  tubes  several  times  alter 
their  size  and  nature. 


Ai  Cortex  limited  on  it*  free  surface  hy  the  capsule;  a,  subcapsular  layer  not 
containing  Malpitfliian  corpuscles ;  a'  inner  stratum  of  cortex  without 
Malpighian  corpuscles ;  b,  lioundary  layer :  c.  papillary  part  next  the 
boundary  layer;  1,  Bowman's  capsule;  2,  neck  of  capsule;  3,  proximal  con- 
voluted tube;  4,  spiral  part;  5,  descending  limb  of  Henle's  loop-tube;  6, 
the  loop  itself  ;  7,  8,  and  9,  the  ascending  linil)  of  Henle's  loop-tube ;  10,  the 
irreu'ular  tubule  ;  11,  the  distal  convoluted  tul)ule  ;  12,  the  first  part  "f  the 
collecting  tube;  13  and  U,  larger  collecting  tube;  in  the  papilla  itself,  not 
represented  here,  the  collecting  tube  joins  others,  and  forms  the  duct. 


360 


Elements  of  Histology 


From  \X>  >tart  to  it^  end  there  is  a  continuous 
fine  memhrana  propria  forming  the  boundary  wall 
of  the  urinary  tubule,  and  this  memhrana  propria  is 
lined  with  a  single  layer  of  ejnthelial  cells  differing  in 


Fig.  236. — From  a  Section  through  the  Cortical  Substance  of  the  Kidney 
of  a  human  Foetus,  showing  a  3Ialpighian  corpuscle.    (HandbooJ:.) 

a.Glomemlu*  ;  6.  tissue  of  the  glomerulus  :  c.  epithelium  covering  the  glomer- 
ulus ;  d,  flattened  epithelium  lining  Bowmans  capsule  ;  e,  the  capsule  itself  ; 
/,  uriniferous  tubules  in  cross  section. 


size,  shape,  and  structure  from  place  to  place  :  in 
the  centre  of  the  tubule  is  a  lunifn,  differing  in  size 
according  to  the  size  of  the  tubule. 

305,  (1)  Each  Mcdpigldan  corpuscle  (Fig.  236) 
is  composed  of  the  capsule — the  <-apsv.le  of  Bou-man — 
and  the  glomerulus,  or  Malpighian  tuft  of  capillary 
blood-vessels. 

The  capsule  of  Bowman  is  a  hyaline  membrana 
propria,  supported,  as  mentioned  aljove,  by  a  small 
amount   of  connective  tissue.     On  its    inner  surface 


Kidney,   Ureter  and  Bladder.         361 

there  is  a  continuous  layer  of  nucleated  epithelial 
cells,  in  the  young  state  of  polyhedral  shape,  in  the 
adult  state  squamous. 

The  glomerulus  is  a  network  of  convoluted 
capillary  blood-vessels  separated  from  one  another 
by  scanty  connective  tissue,  chiefly  in  the  shape 
of  a  few  connective-tissue  corpuscles.  The  capil- 
laries are  grouped  together  in  two  to  five  lobules. 
The  whole  surface  of  the  glomerulus  is  lined  with 
a  delicate  membrana  propria,  and  a  continuous  layer 
of  nucleated  epithelial  cells,  polyhedral,  or  even 
columnar  in  the  young,  squamous  in  the  adult  state. 
The  membrana  propria  and  epithelium  dip  in,  of 
course,  between  the  lobules  of  the  glomerulus,  and 
represent  in  reality  the  visceral  layer  of  the  capsule 
of  the  Malpighian  corpuscle,  the  capsule  of  Bowman 
being  the  parietal  layer.  The  glomerulus  is  connected 
at  one  pole  with  an  afferent  and  efferent  arterial  vessel, 
the  former  being  the  larger  of  the  t^vo. 

Between  Bowman's  capsule  and  the  glomerulus 
there  is  a  space,  the  size  of  which  difiers  according 
to  the  state  of  secretion,  being  chiefly  dependent  on 
the  amount  of  fluid  present. 

The  Malpighian  corpuscles  are  distributed  in  the 
labyrinth  of  the  cortex  only,  with  the  exception  of  a 
thin  peripheral  layer  near  the  outer  capsule,  and  a 
still  thinner  layer  near  the  boundary  layer.  The 
Malpighian  corpuscles  near  the  boundary  layer  are 
the  largest,  those  near  the  periphery  the  smallest  ;  in 
the  human  kidney  their  mean  diameter  is  about  -^^-^ 
of  an  inch. 

306.  (2)  On  the  side  opposite  to  that  where  the 
afferent  and  efferent  arterioles  join  the  glomerulus, 
the  capsule  of  Bowman  passes  through  a  narrow  neck 
into  the  cylindrical  urinary  tubule  in  such  a  way 
that  the  membrana  propria  and  epithelium  of  the 
capsule  are  continued  as   the  membrana  proj^ria  and 


36; 


Elements  of  Histology 


lining    epithelium    of    the    tubule    respectively,    an<l 
the    space    between    the     ca[)sule     of    Bowman     and 


"@t,;;,;^.  :.:;:^V  ,Cr^^^^ 


Fig.  237. — From  a  Vertical  Section  througli  tlie  Kidney  of  Dog,  showing 
jiart  of  the  labyrintli  ami  the  adjoining  medullary  ray.     {Atlas.) 

a.  Capsule  of  Bowman  ;   tlie    capillaries    of    the  glomerulus  are  arranged  in 
lobules;  n,  neck  of  capsule;  b,  irregular  tubule;  c,  proximal   convoluted 
tubules  ;  d,  collecting  tube  ;  e,  part  of  the  spiral  tubule  :  /,  portion  of  the 
-  ascending  limb  of  Henle's  loop-tube ;  d,  e,f,  form  the  meduliarj-  ray. 


the  glomerulus  becomes   the  cavity  or  lumen  of  the 
urinary  tubule. 

307.  (3)  After  it  has  passed  the  neck,  the  urinary 
tubule  becomes  convoluted  ;  this  is  the  joroximal  con- 


K/DXKV,   Ureter  axd  Bladder.  363 

vohded  tubule  (Fig.  237).  It  is  of  considerable  length 
and  is  situated  in  tlie  labyrinth.  It  has  a  distinct 
lumen,  and  its  epithelium  is  a  single  layer  of  polyhedral 
or  short,  columnar,  angular,  or  club-shaped  cells,  each 
with  a  spherical  nucleus.  These  cells  commence  gene- 
rally at  the  neck,  but  in  some  animals — e.g.  in  the 
mouse — they  already  have  begun  in  the  ]N[alpighian 
corpuscle.  The  outer  part  of  the  cell  protoplasm  —  i.e. 
next  the  membrana  propria — is  distinctly  striated, 
owing  to  the  presence  of  rod-shaped  fibrils  (Heiden- 
hain)  vertically  arranged.  The  inner  part  of  the  cell 
substance — i.e.  between  the  nucleus  and  the  inner 
free  matgin — appears  granular.  Epithelial  cells  the 
protoplasm  of  which  possesses  the  above  rod-shaped 
tibrils  will  in  the  following  paragraphs  be  spoken  of 
as  fibrillated  cells. 

The  proximal  convoluted  tuVje  appears  sometimes 
thicker  than  at  other  times  :  in  the  first  case,  its 
lumen  is  smaller,  but  its  lining  epithelial  cells  are 
distinctly  more  columnar.  This  state  is  probably 
connected  with  the  state  of  secretion. 

308.  (4)  The  convoluted  tube  passes  into  the 
spiral  tuhule  (Schachowa).  This  differs  from  the 
former  in  being  situated  not  in  the  labyrinth,  but  in 
a  medullary  ray,  in  which  it  forms  one  conspicuous 
element,  and  in  not  being  convoluted,  but  more  or 
less  straight,  slightly  wavy,  and  spiral.  Its  thickness 
and  lumen  are  the  same  as  in  the  former :  its 
epithelium  is  a  single  layer  of  polyhedral  cells,  with 
distinct  indication  of  tilirillation. 

309.  (5)  Precisely  at  the  line  where  the  cortex 
joins  the  boundaiy  layer,  the  spiral  tube  becomes, 
suddenly  greatly  reduced  in  thickness  ;  it  becomes  at 
the  same  time  very  transparent ;  its  lumen  is  distinct; 
its  membrana  propria  is  now  lined  with  a  single 
layer  of  scales,  each  with  an  oval  llattened  nucleus. 
This  altered    tubule    is   the    descending   loop-tube   of 


364  Elements  of  Histology. 

Henle,  and  it  pursues  its  course  in  the  boundary 
layer  as  a  straight  tuljule,  in  the  continuation  of  the 
medullary  ray. 

In  aspect  and  size  this  part  of  the  urinary 
tul)ule  resembles  a  capillary  blood-vessel,  but  differs 
from  it  inasmuch  as,  in  addition  to  the  lining  laver 
of  flattened  epithelial  cells,  it  possesses  a  membrana 
propria. 

31u.  (6)  The  so-constituted  descending  Henle's 
loop-tube  passes  the  line  between  the  boundary  layer 
and  papillary  portion,  and  having  entered  this  latter, 
pursues  its  course  for  a  short  distance,  when  it  sharply 
bends  backwards  as  the  looi)  of  Henle's  tube ;  it  now 
runs  back  towards  the  boundary  layer,  and  precisely 
at  the  point  of  entering  this  becomes  suddenly  enlarged. 
Up  to  this  point  the  structure  and  size  of  the  loop  are 
exactly  the  same  as  those  of  the  descending  limb. 

311.  (7  and  8)  Having  entered  the  boundary  layer 
it  pursues  its  course  in  this  latter  to  the  cortex  in  a 
more  or  less  straiglit  direction  within  the  medullary 
ray  as  the  ascending  loop-tube.  Besides  being  bigger 
than  the  descending  limb  and  the  loop,  its  lumen  is 
comparativelv  smaller,  and  its  lining  epithelium  is  a 
layer  of  polyhedral,  distinctly  librillated  epithelial 
cells.  The  tube  is  not  quite  of  the  same  thickness  all 
along  the  boundarv  layer,  but  is  broader  in  the  inner 
than  in  the  outer  half ;  besides,  the  tube  is  not  quite 
straight,  but  slightly  wavy  or  even  spiral. 

(9)  Having  reached  the  cortex,  it  enters  this  as 
the  cortical  part  of  the  ascending  loop-tube,  forming 
one  of  the  tubes  of  a  medullary  ray  ;  it  is  at  the  same 
time  narrower  than  in  the  boundary  layer,  and  is 
more  or  less  straiiiht  or  wavv.  Its  lumen  is  verv 
minute,  its  lining  cells  are  flat  polyhedral  witli  a 
small  flattened  nucleus,  and  there  is  an  indication  of 
librillation  (Fig.  237). 

(10)  Sooner  or  later  on  its  way  in  the  cortex  in 


Kidney^   Ureter  and  Bladder.  365 

a  medullary  ray  it  leaves  this  latter  to  enter  the 
labyrinth,  where  it  Avinds  between  the  convoluted 
tubes  as  an  angular  irregular  tubule  (Fig.  237).  Its 
shape  is  very  irregular,  its  size  alters  from  place 
to  place,  its  lumen  is  very  minute,  its  epithelium  a 
layer  of  polyhedral,  pyramidal,  or  short  columnar  cells 
— according  to  the  thickness  of  the  tube  ;  each  cell 
possesses  a  flattened  oval  nucleus  next  to  the  lumen, 
and  a  very  coarsely  and  conspicuously  tibrillated 
protoplasm. 

312.  (11)  This  irregular  tubule  passes  into  the 
distal  convoluted  tubule  or  intercalated  tubule  of 
Schweigger  Seidel.  This  forms  one  of  the  convoluted 
tubes  of  the  labyrinth,  and  in  size,  aspect,  and 
structure  is  identical  with  the  proximal  convoluted 
tubule. 

(12)  The  distal  convoluted  tube  passes  into  a 
short,  thin,  more  or  less  curved  or  wavy  collecting 
tubule,  lined  with  a  layer  of  transparent,  flattened, 
polyhedral  cells  ;  this  is  still  contained  in  the 
labyrinth. 

(13)  This  leads  into  a  somewhat  larger  straight 
collecting  tube,  lined  with  a  layer  of  transparent  poly- 
hedral cells  and  with  distinct  lumen.  This  tube 
forms  part  of  a  medullary  ray,  and  on  its  way  to  the 
boundary  layer  takes  up  from  the  labyrinth  numerous 
curved  collecting  tubules. 

(14)  It  then  passes  unaltered  as  a  straight  collect- 
ing tube  through  the  boundary  layer  into  the  papillary 
portion. 

313.  In  this  part  these  tubes  join  under  acute 
angles,  thereby  gradually  enlarging.  They  run  in  a 
straight  direction  towards  the  apex  of  the  papilla, 
and  the  nearer  to  this,  the  fewer  and  the  bigger  they 
become.  These  are  the  ducts  or  tubes  of  Bellini. 
They  finally  open  on  the  apex  into  a  calix.  The  lumen 
and    the  size  of   the  lining  epithelial  cells — namely, 


;66 


Elements  of  Histology. 


i.^j-'-r-.-^-^^^^a^ 


Fig.  23S. — Diagram  of  the  Vessels 
of  the  Kidney.  {Ludicig,  in 
Strieker's  Manual.) 


whether  more  or  less  co- 
lumnar— are  in  direct  re- 
lation to  the  size  of  the 
coUectinQ'  tube.  The  sub- 
stance  of  the  epithelial 
cells  is  a  transparent  pro- 
toplasm, and  the  nucleus  is 
more  or  less  oval. 

314.  In  many  places 
nucleated  cells,  spindle- 
shaped  or  branched,  can  be 
traced  from  the  membrana 
propria  of  the  tubule  be- 
tween the  lining  epithe- 
lium ;  and,  in  some  cases, 
even  a  delicate  nucleated 
membrane  can  be  seen 
lininor  the  surface  of  the 
epithelium  next  the  lumen. 
In  the  frog,  the  epithelium 
lining,  the  Malpighian  cor- 
puscles, and  the  exceed- 
ingly long  neck  of  the 
urinary  tubule,  are  pos- 
sessed of  lonij  hlamentous 
ciHa,  rapidly  moving  during 
life.  In  the  neck  of  some 
of  the  urinary  tubules  in 
mammals  there  is  also  an 
indication  of  cilia  to  be 
noticed. 


«/,  Interlobular  artery  ;  vi,  interlobular 
vein :  g.  glomerulus  of  Malpighian 
corpuscle;  vs.  vena  stellata;  ar, 
arteriiB  rectas  :  rr,  vena;  rects  ;  ob, 
Imndle  of  arteria;  rectae:  rb.  bundle 
of  venffi  rectse  ;  rp,  network  of  vessels 
around  the  nioutti  of  the  ducts 
at  the  apex  of  the  papillK. 


K/DN/:v,    Ureter  and  B [.adder. 


367 


Heideiihaiii  lias  sliown  tliat  indigo-sulphate  of 
sodium,  injected  into  the  circulating  blood  of  the  dog 
and  rabbit,  is  excreted  through  certain  parts  of  tlie 
urinary  tubules  only — viz.  those  which  are  lined  with 


r  V:  '-'v  yf. 


P 


t 


"-^^k:-^  ■-'V.v.  ■■^•■-^■^  "^  -'"-S:' 

.■>»•/  -J     .  .,-     '/•     -.  .     ^. 

*     •.■■••  '■%  ..    ■ .  .     (.  , «     ,, 

/  *    .1        •'     1' 


Fig.  239. — Vertical  Section  through  the  entire  Kidney  (injected)  of  a  Rat. 
{Photo.     Low  Power.) 

(I,  Cortex  ;  b,  papilla  ;  c,  boundary  layer. 

"fibrillated^'  epithelium.  He  maintains  that  this 
excretion  is  effected  through  the  cell  substance  ;  but, 
in  the  case  of  carmine  being  used  as  pigment,  I  have 
not  found  the  excretion  to  take  place  through  the 
substance  of  the  epithelial  cells,  but  through  the 
homogeneous  interstitial  or  cement  substance  between 
the  epithelial  cells. 

315.  11.   The  blood-vessels.  (Figs.  238  and  239). 


568  Elements  of  Histology. 

The  large  branches  of  the  renal  artery  and  vein 
are  situated  in  the  submucous  tissue  of  the  pelvis, 
and  they  enter,  or  pass  out  respectively  from,  the  part 
of  the  parenchyma  corresponding  to  the  junction  of 
the  cortex  and  boundary  layer,  where  they  follow  a 
more  or  less  horizontal  course,  and  give  off,  or  take  up 
respectively,  smaller  branches  to  or  from  tlie  cortex 
and  medulla. 

(1)  In  the  cortex  the  arterial  trunks  give  off  to 
the  cortex  small  branches,  which  singly  enter  the 
lahijrinth  in  a  direction  vertical  to  the  surface  of  the 
kidney.  These  are  the  interlohidar  arteries.  Each  of 
these,  on  its  way  towards  the  external  capsule  of  the 
kidney,  gives  off,  on  all  sides  of  its  circumference, 
shorter  or  longer  lateral  branches  :  these  are  the 
afferent  arterioles  for  the  Malpighian  corpuscles,  each 
one  entering  a  Malpighian  corpuscle  and  breaking  up 
into  the  capillaries  of  the  glomerulus. 

On  their  way  towards  the  external  capsule,  the 
arteries  become  greatly  reduced  in  size,  and  finally 
enter  the  capillary  network  of  the  most  peripheral 
part  of  the  cortex  ;  but  some  of  these  arterioles  may 
be  also  traced  into  the  outer  capsule,  where  they 
become  connected  with  the  capillary  networks  of  this 
latter.  The  efferent  vessel  of  a  Malpighian  glome- 
rulus at  once  breaks  up  into  a  dense  network  of 
capillary  blood-vessels,  which  surround  in  all  direc- 
tions the  urinary  tubules  of  the  labyrinth.  This 
network  is  continuous  with  that  of  the  capillaries  of 
the  medullar}^  I'ays,  the  meshes  being  here  elongated, 
and  the  capillary  blood-vessels,  for  obvious  reasons, 
more  of  a  straight  arrangement.  The  capillaries  of 
the  whole  cortex  form  one  continuous  network. 

316.  The  veins  which  take  up  the  blood  from  this 
network  are  arranged  in  this  manner  : — ^There  are 
formed  venous  vessels  underneath  the  external 
capsule,   taking    up    like    rays    on    all    sides,   minute 


Kidney,    Urkter  and  Bladder.  369 

radicles  connected  with  the  capillaries  of  the  most 
peripheral  ^Axt  of  tlie  cortex.  These  are  the  venoi 
steUata; ;  they  pass  into  the  labyrinth  of  the  cortex, 
where  they  follow  a  vertical  course  in  company  with 
the  interlobular  arteries.  On  tliis  passage  the}?"  com- 
municate with  the  capillaries  of  the  labyrinth,  and 
ultimately  open  into  the  large  venous  branches 
situated  between  cortex  and  boundary  layer. 

317.  (2)  In  the  medulla.  From  the  large  arterial 
trunks  short  branches  come  off,  w^hich  enter  the 
boundary  layer,  and  there  split  up  into  a  bundle 
of  minute  arterioles,  which  pass  in  a  straight  direc- 
tion vertically  through  the  boundary  layer  into  the 
papillary  portion.  These  are  the  arterim  recUt 
(Fig.  238).  The  number  of  vessels  of  each  bundle 
is  at  the  outset  increased  by  the  efferent  vessel  of 
the  Malpighian  corpuscles  nearest  to  the  boundary 
layer. 

On  their  way  through  the  boundary  layer,  and 
through  the  papillary  portion  of  the  medulla, 
these  arterioles  give  off  the  capillary  netw^ork  for 
the  urinary  tubules  of  these  parts,  the  network, 
for  obvious  reasons,  possessing  an  elongated  arrange- 
ment. 

From  this  network  originate  everywhere  minute 
veins,  which  on  their  way  towards  the  cortical  margin 
increase  in  size  and  number  ;  they  form  also  bundles 
of  straight  vessels — vence  rectca — and  ultimately  enter 
the  venous  trunks  situated  between  the  boundary 
Jayer  and  cortex. 

The  bundles  of  the  arterise  rectae  and  venae  rectse 
form  severally,  in  the  boundary  layer,  the  transparent 
striae  mentioned  on  a  previous  page  as  alternating 
with  the  opaque  striae,  these  latter  being  bundles  of 
urinary  tubules. 

At  the  apex  of  each  papilla  there  is  a  network  of 
capillaries  around  the  mouth  of  each  duct. 


J)  / 


Elements  of  Histology. 


318.  The  outer  capsule  of  the  ki(hiey  contains  a 
network  of  capillary  blood-vessels  ;  the  arterial 
branches  leading  into  them  are  derived  from  two 
sources  :  («)  from  the  outrunners  of  the  interlobular 


Fig.  240.— From  Transverse  Section  through  Urinary  Bladder  of  Dog. 
{Photo.     Low  Pov:er.) 

a,  Inner  surface  of  folded  mucous  membrane,  covered  with  stratified  transitional 
epithelium ;  b,  raucous  membrane :  c,  outer  coat  of  non-striped  muscle. 


arteries  of  the  cortex,  and  (b)  from  extra-renal  arteries. 
The  veins  lead  [a)  into  the  vena?  stellatie,  and  (b)  into 
extra-renal  veins. 

The  li/mpJtatic  vessels  form  a  plexus  in  the  capsule 
of  the  kidney.  They  are  connected  with  lymph  spaces 
between  the  urinary  tubes  of  the  cortex.  The  large 
blood-vessels  are  surrounded  by  a  plexus  of  lym- 
phatics,  which    take    up  lymph  spaces   between    the 


KlDNKV,     UrKTER    and    B LADDER.  37  1 

urinary  tubules,  both  in  the  cortex  and  the  boundary 
layer. 

oil*.  The  ureter  is  lined  with  stratified  transi- 
tional e]>itlieliam.  Underneath  this  is  the  mucosa, 
a  connective-tissue  membrane  with  capillary  blood- 
vessels. The  submucosa  is  a  loose  connective  tissue. 
Then  follows  a  muscular  coat  composed  of  non- 
striped  muscular  tissue,  arranged  as  an  inner  and 
outer  longitudinal  and  a  middle  circular  coat.  Then 
follows  an  outer  limiting  thin  tibrous  coat  or  adventitia. 
In  this  last  have  been  observed  minute  cjanfjlia  in 
connection  with  the  nerve-branches. 

320.  The  bladder  is  similar  in  structure,  but 
the  mucous  membrane  and  muscular  coat  are  very 
much  thicker.  In  the  latter,  which  consists  of  non- 
striped  fibres,  can  be  distinguished  an  inner  circular, 
a  middle  oblique,  and  an  outer  longitudinal  stratum. 
The  last  is  best  developed  in  the  fundus  (Fig.  2-10). 

Xumerous  sympathetic  ganglia,  of  various  sizes, 
are  found  in  connection  with  the  nerve-branches 
underneath  the  adventitia  (peritoneal  covering),  and 
in  the  muscular  coat  (F.  Darwin).  The  epithelium 
lining  the  bladder  is  stratified  transitional,  and  it 
greatly  varies  in  the  shape  of  its  cells  and  their 
stratification,  according  to  the  state  of  expansion  of 
the  bladiler. 


172 


CHAPTER    XXXIII. 

THE     xMALE     GENITAL     ORGANS. 

321.  (1)  The  testis  of  man  and  mammals  is  en- 
veloped in  a  capsule  of  white  fibrous  tissue,  the  tunica 
adnata.  This  is  the  visceral  layer  of  the  tunica 
vaginalis.  Like  the  parietal  layer,  it  is  a  serous 
membrane,  and  is  therefore  covered  with  endo- 
thelium. Minute  villi  are  occasionally  seen  pro- 
jecting from  this  membrane  into  the  cavity  of 
the  tunica  vaginalis.  These  villi  are  generally 
covered  with  germinating  endothelium.  Inside  the 
tunica  adnata,  and  firmly  attached  to  it,  is  the 
tunica  cdbnginea,  a  fibrous  connective-tissue  mem- 
brane of  lamellar  structure.  Towards  the  posterior 
maro-in  of  the  human  testis  its  thickness  increases, 
and  forms  there  (Fig.  241)  a  special  accumu- 
lation— in  cross  section  more  or  less  conical,  with 
posterior  basis — the  mediastinum  testis,  or  corpus 
Highmori. 

Between  the  tunica  adnata  and  tunica  albuginea 
is  a  rich  plexus  of  lymphatics,  which,  on  the  one  hand, 
takes  up  the  lymphatics  of  the  interior,  and  on  the 
other  leads  into  the  efferent  vessels  that  accompany 
the  vas  deferens. 

The  testis  of  the  dog,  cat,  bull,  pig,  rabbit,  etc., 
have  a  central  corpus  Highmori ;  that  of  the  mole, 
hedgehog,  and  bat  a  peripheral  one ;  while  that  of 
the  rat  and  mouse  have  none  (Messing). 

322.  The  framework.  —  From  the  anterior 
margin    of    the    corpus     Highmori    spring    numerous 


Male  Genital  Organs. 


373 


septa  of  connective  tissue,  which,  passing  in  a  radiat- 
ing direction  towards  the  alhuginea,  with  which  tliey 
form  a  continuity,  sul)divide   the  testis  into  a  large 


a^ 


Fig.    241.— Passage    of   Convoluted  Seminiferous  Tubules  into  Straight 
Tubules  and  into  the  Rete  Testis.     {Mihalkovics,  Quain's  "  Anatomy.")  ^ 
a,  Seminiferous  tubules  ;  b,  fibrous  tissue  :  c,  rete  testis. 

number  of  more  or  less  conical  compartments,  or 
lobules,  the  basis  of  which  is  situated  at  the  tunica 
albuginea,  the  apex  at  the  corpus  Highmori.    Kolliker 


374  Elements  of  Histology. 

mentions  that  non-striped  muscular  tissue  occurs  in 
these  se[)ta. 

From  these  septa  thin  connective-tissue  lamellte 
pass  into  the  compartments,  and  they  form  the 
supporting  tissue  for  the  blood-vessels,  and  also 
represent  the  interstitial  connective  tissue  between 
the  seminal  tubules. 

This  intertubular  or  interstitial  tissue  is  distinctly 
iamellated,  the  lamella?  being  of  different  thicknesses, 
and  consisting  of  thin  bundles  of  fibrous  connective 
tissue — arranged  more  or  less  as  fenestrated  mem- 
branes— and  endotheloid  connectixe  plates  on  their 
surface.  Between  the  lamella?  are  left  spaces,  and 
these  form,  through  the  fenestra?  or  holes  of  the 
lamellae,  an  intercommunicating  system  of  lymph 
spaces — being,  in  fact,  the  rootlets  of  the  lymphatics 
(Ludwig  and  Tomsa). 

AVithin  the  lamellae  are  found  peculiar  cells, 
which  are  much  larger  than  lymph  cells,  and  which, 
in  some  instances  {e.g.  guinea-pig),  include  pigment 
granules.  They  contain  a  spherical  nucleus.  In  man, 
dog,  cat,  sheep,  especially  in  the  boar,  these  cells  form 
large,  continuous  groups — plates  and  cylinders — and 
the  cells  are  polyhedral,  and  exactly  similar  to  epithe- 
lial cells.  They  are  separated  from  one  another  within 
the  grouj:)  by  a  thin  interstitial  cement  substance. 
Their  resemblance  with  epithelium  is  complete.  They 
are  remnants  of  the  epithelial  masses  of  the  Wolffian 
body  of  the  fcetus. 

323.  The  seminal  tiibiile!^  (Fig.  242).  — 
Within  each  compartment,  above  mentioned,  lie 
numerous  seminal  tubules,  twisted  and  convoluted 
in  many  ways,  and  extending  from  the  periphery  to 
near  the  corpus  Highmori.  The  tubules,  as  a  rule, 
are  rarely  branched ;  but  in  the  young  state,  and 
especially  towards  the  periphery,  branching  is  not 
uncommon. 


Male  Genital   Organs. 


375 


Each  seminal  tubule  consists  of  a  membrana 
propria,  a  lining  epith(4iuin,  and  a  lumen.  The 
membrana  propria  is  a  hyaline  membrane,  with  oval 
nuclei  at  regular  intervals.  In  man  it  is  thick  and 
lamellated,  several  such  nucleated  membranes   being 


Fig.  242.— Section  of  parts  of  three  Seiniuiferous  Tubules  of  Rat. 
(£.  A.  ScMfer.) 

a,  "With  the  spermatozoa  least  advanced  in  development;  &,  more,  and  c,  most 
advanced.    Between  the  tubules  are  strands  of  interstitial  cells. 


superimposed  over  one  another.  The  lumen  is  in 
all  tubes  distinct  and  relatively  large.  The  lining 
epithelium,  or  the  seminal  cells,  differ  in  the  adult 
in  ditferent  tubules,  and  even  in  different  parts  of 
the  same  tubule,  being  dependent  on  the  state  of 
secretion. 

324.  Before  puberty  all  tubules  are  uniform  in 
this  respect,  being  lined  with  two  or  three  layers  of 
polyhedral    epithelial    cells,    each    with    a    spherical 


376 


Elements  of  Histology. 


nucleus.       After     puberty,   however,     the     following 
different  t3qies  can  be  distinguished. 

(a)  Tubules  or  parts  of  tubules  similar  to  those 
of  the  young  state — viz.  several  layers  of  polyhedral 
epithelial  cells  lining  the  menibrana  propria.  These 
are  considered  as  («)  the  outer  and  ih)  the  inner 
seminal  cells.      The  former  are  next  to  the  membrana 


Fk 


'243 


-From  a  Section  through  the  Testis  of  Dog,  showing  portions  of 
three  seminal  tubules.     {Atlas.) 

j»,  Seminal  epithelial  cells  and  mimerous  small  cellt-  loosely  arranged  ;  B,  small 
cells  or  sperniatohlasts  becoming  converted  into  spermatozoa;  c,  groups  of 
these  in  a  further  stage  of  development. 

propria  ;  they  are  ])olyhedral  in  shape,  transparent, 
and  the  nucleus  of  many  of  them  is  in  the  process 
of  karyomitosis  or  indirect  division  (see  par.  8)  ; 
in  some  the  nucleus  is  oval  transparent,  but  containing 
a  distinct  network.  The  inner  seminal  cells  generally 
form  two  or  three  layers,  and  are  more  loosely  con- 
nected with  one  another  than  the  outer  seminal  cells, 
and  therefore   possess    a    more    rounded    appearance. 


Male  Genital  Oh  cans.  377 

Between  these  a  nucleated  reticuluiii  of  fine  fibres 
is  sometimes  noticed,  the  i^erm  reticulum  of  von 
Ebner.  But  this  is  merely  a  supporting  tissue,  and  has 
nothing  to  do  with  the  germination  of  the  cells  or  the 
spermatozoa  (Merkel).  The  inner  seminal  cells  show 
very  abundantly  the  process  of  indirect  division  of  the 
nucleus,  almost  all  being  seen  in  one  or  another  phase 
of  it. 

325.  The  division  of  the  inner  seminal  cells  yields 
numerous  small  spherical  cells  ;  these  lie  nearest  the 
lumen,  and  are  very  loosely  connected  vi^ith  one 
another.  It  is  these  which  are  transformed  into 
spermatozoa,  and  hence  are  appropriately  called 
spermatoblasts  (-t'ig.  242). 

Amongst  the  seminal  cells,  especially  of  cat  and 
dog,  are  found  occasionally,  but  not  very  commonly, 
large  multinuclear  cells,  the  nuclei  of  which  are  also 
in  one  or  other  stage  of  karyomitosis. 

(b)  The  innermost  cells — i.e.  the  spermatoblasts — - 
become  pear-shaped,  the  nucleus  being  situated  at  the 
thinner  extremity,  becoming  at  the  same  time  flattened 
and  homogeneous  (Fig.  24.')).  The  elongation  of  the 
spermatoblasts  gradually  proceeds,  and  in  consequence 
of  this  we  find  numerous  elongated,  club-shaped 
spermatoblasts,  each  with  a  flattened  nucleus  at  the 
thin  end.  These  are  the  young  spermatozoa,  the 
nucleated  extremity  being  the  head. 

(c)  At  the  same  time  these  young  spermatozoa 
become  grouped  together  by  an  interstitial  granular 
substance,  in  peculiar  fan-shaped  groups  :  in  these 
groups  the  head — i.e.  the  thin  end  containing  the 
flattened  homogeneous  nucleus — is  directed  towards 
the  inner  seminal  cells,  while  the  opposite  extremity 
is  directed  into  the  lumen  of  the  tube.  Meanwhile 
the  inner  seminal  cells  continue  to  divide,  and  thus 
the  groups  of  young  spermatozoa  get  more  and  more 
buried,  as  it  were,  between  them. 


378  Elements  of  Histology. 

326.  The  original  cell-body  of  the  spermatoblasts 
goes  on  elongating  until  its  protoplasm  is  almost,  but 
not  quite,  used  to  form  a  rod-shaped  middle  -piece 
(Schweigger  Seidel)  of  the  spermatozoa;  from  the 
distal  end  of  this,  a  thin  long  hair-like  filament,  called 
the  tail.,  grows  out.  Where  this  joins  the  end  of  the 
middle  piece,  there  is  present,  even  for  some  time 
afterwards,  a  last  remnant  of  the  granular  cell-body  of 
the  original  spermatoblast.  Some  of  the  inner  seminal 
cells  not  used  for  the  formation  of  spermatozoa  dis- 
integrate and  yield  the  granular  substance  between 
the  spermatozoa  of  the  groups,  and  also  between  these 
latter. 

When  the  granular  interstitial  substance  holding 
together  the  spermatozoa  of  a  group  has  become  dis- 
integrated, the  spermatozoa  are  isolated.  \\'hile  this 
development  of  the  spermatozoa  goes  on,  the  inner 
seminal  cells  continue  to  produce  spermatoblasts,  some 
of  which  are  converted  into  spermatozoa. 

327.  Spermatozoa  (Fig.  24-4). — Fully  formed 
spermatozoa  of  man  and  mammals  consist  of  a  homo- 
geneous flattened  and  slightly  con\-ex-concave  head 
(the  nucleus  of  the  original  spermatoblast),  a  rod- 
shaped  middle  2nece  (derived  directly  from  the  cell- 
body  of  the  spermatoblast),  and  a  long  hair-like  tail. 
While  living,  the  spermatozoa  show  very  rapid  oscilla- 
tory and  propelling  movement,  the  tail  acting  as  a 
Hagellum  or  cilium ;  its  movements  are  sj^iral. 

In  the  newt  there  is  a  tine  spiral  thread  attached 
to  the  end  of  the  long,  curved,  spike-like  head,  and  by 
a  hyaline  membrane  it  is  fixed  to  the  middle  piece ;  it 
extends  beyond  this  as  the  tail.  Also  in  the  mam- 
malian and  human  spermatozoa,  a  similar  spiral  thread, 
closely  attached  to  the  middle  piece,  and  terminating 
as  the  tail,  has  been  observed  (H.  Gibbes). 

328.  The  seminal  tubules  of  each  lobule  pass  into 
a   short    straight    tubuU-.    the    vas   rectum.      This    is 


Male  Genital   Organs. 


379 


narrower  than  tlie  seminal  tubule,  and  is  lined  with  a 
single  layer  of  polyhedral  or  short  columnar  epithelial 
cells.  The  vasa  recta  form,  in  the  corpus  Highmori, 
a  dense  network  of  tubular  channels,  which  are  irregu- 
lar in  diameter,  being  at  one  place  narrow  clefts,  at 


Fig.  244. — Various  Kinds  of  Spermatozoa. 

A,  Spennatr)zoon  of  guinea-pig  not  yet  completely  ripe;  b,  the  same  seen  side- 
ways, the  head  of  the  spermatozoon  is  flattened  from  side  to  side;  c, 
spermatozoon  of  h(jrse ;  d,  spermatozoon  of  newt. 


another  wide  tuljes,  but  never  so  wide  as  the  seminal 
tubules  ;  this  network  of  channels  is  the  rete  testis. 

329.  (2)  The  epidid.vnii«». — From  the  rete  testis 
we  pass  into  the  rasa  eferentia,  each  being  a  tube 
wider  than  those  of  the  rete  testis,  and  each  leading 
into  a  conical  network  of  coiled  tubes.  These  are  the 
coiii  vascalosi.  The  smn  total  of  all  the  coni  vasculosi 
forms  the  globus  major  or  head  of  the  epididymis. 

330.  The  vasa  efferentia  and  the  tubes  of  the  coni 


•So 


Elements  of  Histology. 


vasculosi  are  about  the  size  of  the  seminal  tubules, 
but,  unlike  them,  are  lined  with  a  layer  of  beautiful 
columnar  epithelial  cells,  with  a  bundle  of  cilia  (Fig. 
245).  Outside  these  is  generally  a  layer,  more  or 
less  continuous,  of  small  polyhedral  cells.  The  sub- 
stance of  the  columnar  cells 
is  distinctly  longitudinally 
tibrillated.  The  membrtaia 
propria  is  thickened  by  the 
presence  of  a  circular  layer 
of  non  -  striped  muscular 
fibres.  The  rest — i.e.  the 
globus  minor,  or  tail  of  the 
epididymis — is  made  up  of 
a  continuation  of  the  tubes 
of  the  globus  major,  the 
tubes  diminishing  gradually 
in  number  by  fusion,  and 
thereby  at  the  same  time 
becoming      larger.  The 

columnar    epithelial    cells, 
facing    the    lumen    of    the 
minor,   are    possessed    of    cilia 


Fig.    245.— Tubule    of    the    Epi- 
didymis in  cross-section. 

The  wall  of  the  tubule  is  made  up  of 
a  thick  layer  of  roncentrically  ar- 
ranged n(tn-:<triped  muscular  tissue, 
a  layer  of  columnar  epithelial  cells 
witii  extraoi'diuarily  lonsr  cilia  pro- 
jecting into  the  lumen  of  the  tube. 


tubes    of    the   globus 
of  unusual  length. 

The  tubes  of  the  epididymis  are  separated  from  one 
another  by  a  larger  amount  of  connective  tissue  than 
those  of  the  testis. 

The  tubes  of  the  organ  of  Giralde,  situated  in  the 
beginning  of  the  funiculus  spermaticus,  are  lined  with 
columnar  ciliated  epithelium.  So  is  also  the  pedun- 
culated hydatid  of  Morgagni  attached  to  the  globus 
major, 

331.  The  seminal  tubules  and  the  tubes  of  the 
epididymis  are  surrounded  by  a  rich  network  of 
capillary  blood-vessels.  Between  the  tubes  of  the 
testis  and  epididymis  are  lymph  spaces,  forming  an 
intercommunicating  system,  and  emptying  themselves 


Male  Genital   Organs.  381 

into  the  superficial  networks  of  lymphatics — i.e. 
those  of  the  albuginea ;  the  arrangement  of  these 
networks  is  somewhat  (liferent  in  the  testis  and 
epididymis. 

332.  (3)  Vas  ^leferciis  and  vesiciila?  seiiii- 
iiales. — The  tubes  of  the  globus  minor  open  into  the 
vas  deferens.  This  is,  of  course,  much  larger  than 
the  former^  and  is  lined  with  stratified  columnar 
epithelium.  Underneath  this  is  a  dense  connective- 
tissue  mucosa,  containing  a  rich  network  of  capillary 
blood-vessels.  Beneath  this  mucosa  is  a  thin  sub- 
mucous tissue,  which  in  the  ampulla  is  better  de- 
veloped than  in  other  parts,  and  therefore  allows  the 
mucous  membrane  to  become  folded.  Outside  the 
submucous  tissue  is  the  muscular  coat,  which  consists 
of  non-striped  muscular  tissue,  arranged  as  an  inner 
circular  and  an  outer  longitudinal  stratum.  At  the 
coQimencement  of  the  vas  deferens  there  is  in  addition 
an  inner  longitudinal  layer.  There  is  finally  a  fibrous 
tissue  adventitia.  This  contains  longitudinal  bundles 
of  non-striped  muscular  tissue,  known  as  the  cremaster 
internus  (Henle).  A  rich  plexus  of  veins — plexus 
pampiniformis — and  a  rich  plexus  of  lymphatic  trunks, 
are  situated  in  the  connective  tissue  of  the  spermatic 
cord.  The  plexus  spermaticus  consists  of  larger  and 
smaller  nerve-trunks,  with  which  are  connected  small 
groups  of  ganglion  cells  and  also  large  ganglionic 
swellings. 

333.  In  the  vesiculce  semiiiales  we  meet  with 
exactly  the  same  layers  as  constitute  the  wall  of  the 
vas  deferens,  but  they  are  thinner.  This  refers  espe- 
cially to  the  mucosa  and  the  muscular  coat.  The 
former  is  placed  in  numerous  folds.  The  latter  con- 
sists of  an  inner  and  outer  longitudinal  and  a  middle 
circular  stratum.  The  orano-lia  in  connection  with  the 
nerve  trunks  of  the  adventitia  are  very  numerous. 

334.  In  the  ductus  ejacidatorii  we  find  a  lining  of 


382  Elements  oe  Histology. 

columnar  epithelial  cells ;  outside  of  this  is  a  delicate 
mucosa  and  a  muscular  coat,  the  latter  consisting  of 
an  inner  thicker  longitudinal  and  an  outer  thinner 
circular  stratum  of  non-striped  muscular  tissue. 

When  passing  into  the  vesicula  prostatica  the 
columnar  epithelium  is  gradually  rejDlaced  by  stratified 
pavement  epithelium. 

335.  (4)  The  prostate  inland. — Like  other 
glands,  the  prostate  consists  of  a  framework  and  the 
gland  tissue  proper  or  the  parenchyma. 

The  framework,  unlike  that  of  other  glands,  is 
essentially  muscular,  being  composed  of  bundles  of 
non-striped  muscular  tissue,  with  a  relatively  small 
adndxture  of  fibrous  connective  tissue.  The  latter 
is  chietlv  limited  to  the  outer  capsule  and  the  thin  septa 
passing  inwards,  whereas  the  non-striped  muscular  tis- 
sue surrounds  and  separates  the  individual  gland  alveoli. 

336.  The  pareiicliyiiia  consists  of  the  chief 
ducts,  which  open  at  the  base  of  and  near  the  colli- 
culus  seminalis,  and  of  the  secondary  ducts,  minor 
brandies  of  the  former,  which  ultimately  lead  into  the 
alveoli.  These  are  longer  or  shorter,  wavy  or  con- 
voluted branched  tubes  with  numerous  saccular  or 
club-shaped  branches.  The  alveoli  and  ducts  are 
limited  by  a  membrana  propria,  have  a  distinct  lumen, 
and  are  lined  with  columnar  epithelium.  In  the 
alveoli  there  is  only  a  single  layer  of  beautiful 
columnar  epithelial  cells,  the  substance  of  which  is 
distinctly  and  longitudinally  striated.  In  the  ducts 
there  is  an  inner  layer  of  short  columnar  cells,  and  an 
outer  one  of  small  cubical,  polyhedral  or  spindle- 
shaped  cells. 

At  the  mouth  of  the  ducts  the  stratified  pavement 
epithelium  of  the  pars  prostatica  of  the  urethra  passes 
a  short  distance  into  the  duct. 

The  alveoli  are  surrounded  by  dense  networks  of 
capillary  blood-vessels. 


Male  Genital   Organs.  383 

In  the  pei-iplieral  portion  of  the  gland  numerous 
ganglia  are  inter[)Osed  in  the  rich  plexus  of  nerves. 
Also  Pacinian  corpuscles  are  to  be  met  with. 

337.  (T))  TIk'  iii-<'tlirsi. — The  mucous  membrane 
of  the  male  uiethra  is  lined  with  simple  columnar 
epithelium,  except  at  the  commencement— the  pars 
prostatica — and  at  the  end — the  fossa  navicularis — 
where  it  is  stratified  pavement  epithelium. 

The  mucous  membrane  is  fibrous  tissue  with  very 
numerous  elastic  fibres.  Outside  of  it  is  a  muscular 
coat  composed  of  non-striped  muscular  tissue,  and 
arranged  as  an  inner  circular  and  an  outer  longi- 
tudinal stratum,  except  in  the  pars  prostatica  and  pars 
membranacea,  where  it  is  chiefly  longitudinal.  In  the 
latter  portion  the  muscular  bundles  pass  also  into  the 
mucous  membrane,  where  they  follow  a  longitudinal 
course  between  large  veins  arranged  in  a  longitudinal 
plexus.  These  veins  empty  themselves  into  small 
etTerent  veins.  This  plexus  of  large  veins  with  the 
muscular  tissue  between  represents  a  rudiment  of  a 
cavernous  tissue  (Henle). 

The  mucous  membrane  forms  peculiar  folds  sur- 
rounding the  lacunas  Morgagni.  There  are  small 
mucous  glands,  lined  with  columnar  epithelium, 
embedded  in  the  mucous  membrane ;  they  open  into 
the  cavity  of  the  urethra  and  are  known  as  Littre's 
glands. 

338.  (6)  The  ^landfi»  of  Cowper. — Each  gland 
of  Cowpei"  is  a  large  compound  tubular  gland,  which, 
as  regards  structure  of  ducts  and  alveoli,  resembles  a 
mucous  gland.  The  wall  of  the  chief  ducts  possesses 
a  large  amount  of  longitudinally  arranged  non-striped 
muscular  tissue.  The  epithelium  lining  the  ducts  is 
composed  of  columnar  cells.  The  alveoli  possess  a 
large  lumen  and  are  lined  with  columnar  mucous 
cells,  the  outer  portion  of  the  cell  being  distinctly 
striated  (Langerhans).     In  the  cell  the  reticulum  is 


384  Elements  of  Histology. 

also  distinct.  In  this  respect  the  alveoli  completely 
resemble  those  of  the  submaxillary  of  the  dog,  but 
there  are  no  real  crescents  in  the  alveoli  of  Cowper's 
gland. 

339.  (7)  Tlie  corpus  «ipoiig'io«^iiiii. — The  cor- 
pus spongiosum  of  the  urethra  is  a  continuation  of 
the  rudimentary  corpus  cavernosum  above-mentioned 
in  connection  with  the  pars  membranacea  of  the 
urethra.  It  is  essentially  a  plexus  of  large  veins 
arranged  chiefly  longitudinally,  and  leading  into 
small  efferent  veins.  Between  the  laro^e  veins  are 
bundles  of  non-striped  muscular  tissue.  The  capillary 
blood-vessels  of  the  raucous  membrane  of  the  urethra 
open  into  the  veins  of  the  plexus.  The  outer  portion 
of  the  corpus  spongiosum,  including  the  bulbus 
urethn^,  shows,  however,  numerous  venous  sinuses, 
real  caverna?,  into  which  open  capillary  blood- 
vessels. 

340.  The  glaiis  penis  is  of  exactly  the  same 
structure  as  the  corpus  spongiosum.  The  outer 
surface  is  covered  with  a  delicate  fibrous  tissue 
membrane,  ^^•hich  on  its  free  surface  bears  minute 
papillae,  extending  into  the  stratified  pavement  epi- 
thelium. At  the  corona  glandis  exist  small  sebaceous 
follicles,  the  glands  of  T3^son ;  they  are  continued 
from  the  inner  lamella  of  the  prepuce,  where  they 
abound.  The  papilla?  of  the  glans  contain  loops  of 
capillary  blood-vessels.  Plexuses  of  non-medullated 
nerve  fibres  are  found  underneath  the  epithelium  of 
the  surface  of  the  glans.  With  these  are  connected 
the  end  bulbs  described  in  a  former  chapter  as  the 
genital  nerve-end  corpuscles. 

341.  (8)  Tlie  corpora  cavernosa  penis. — 
Each  corpus  cavernosum  is  enveloped  in  a  fibrous 
capsule,  the  albuginea,  made  up  of  lamellae  of  fibrous 
connective  tissue.  Numerous  Pacinian  corpuscles 
are  met  with   around  it.      The  matrix  of  the  corpus 


Male  CiEnital  Okgans.  385 

cavernosiun  consists  of  trabecular  of  fibrous  tissue, 
between  wliicli  pass  bundles  of  non-striped  muscular 
tissue,  all  in  different  directions.  Innumerable 
cavernie  or  sinuses,  intercommunicating  with  one 
anotlier,  are  present  in  this  matrix,  capaljle  of  such 
considerable  repletion  that  in  the  maximum  degree 
of  this  state  the  sinuses  are  almost  in  contact,  and 
the  trabeculaj  compressed  into  very  delicate  septa. 
The  sinuses  are  lined  with  a  single  layer  of  flattened 
endothelial  plates,  and  their  wall  in  many  places  is 
strengthened  by  the  bundles  of  non- striped  muscular 
tissue.  The  sinuses  during  erection  become  filled 
with  blood,  being  directly  continuous  with  capillary 
blood-vessels.  These  are  derived  from  the  arterial 
branches  which  take  their  course  in  the  above  tra- 
beculae  of  the  matrix.  The  blood  passes  from  the 
sinuses  into  small  efferent  veins.  But  the  blood 
passes  also  directly  from  the  capillaries  into  the 
efferent  veins,  and  this  is  the  course  the  blood  takes 
under  passive  conditions,  while  during  erection  it 
passes  chiefly  into  the  above  sinuses. 

342.  In  the  peripheral  part  of  the  corpus  caver- 
nosum  there  exists  a  direct  communication  between 
the  sinuses  and  minute  arteries  (Langer),  but  in  the 
rest  the  arteries  do  not  directly  communicate  with 
the  sinuses  except  through  the  capillary  blood- 
vessels. In  the  passive  state  of  the  corpus  caver- 
nosum,  the  muscular  trabecular  forming  part  of  the 
matrix  are  contracted,  and  the  minute  arterial 
branches  embedded  in  them  are  therefore  much 
coiled  up  ;  these  are  the  arterise  helicina3. 


;S6 


CHAPTER  XXXIY. 


THE    FEMALE    (GENITAL    ORGANS. 


343.  (1)  The  ovary  (Fig.  24G). — In  tlie  ovary, 
as  in  other  glands,  the  framework  is  to  be  dis- 
tinguished from 
the  parenchyma. 
In  the  part  of 
the  ovary  next 
to  the  hilum  there 
are  numerous 
blood-vessels,  in 
a  loose  fibrous 
connective  tissue, 
with  numerous 
longitudinal  bun- 
dles of  non-striped 
muscular  tissue 
directly  contin- 
uous with  the 
same  tissues  of 
the  lioamentum 
latum.  This  por- 
tion of  the  ovary 
is  the  zona  vas- 
culosa  (Wal- 
deyer).  All  parts 
of  the  zona  vas- 
culosa  —  i.e.  the 
bundles  of  tibrous 
connective  tissue, 
the  blood-vessels,  and  the  bundles  of  non-striped 
muscular  tissue— are  traceable  into";  the  parenchyma. 


Fig.:  246.— Vertical  Section  through  Ovary  of 

half -grown  Cat.  {Atlas. ) 
fi,  Albuginea;  the  geminal  epitlieliuia  i3  not 
distinguishable  owing  to  the  low  power  under 
which  the  section  is  supposed  to  be  viewed;  0, 
layer  of  smallest  Graaflan  follicles  and  ova;  c, 
medium-sized  follicles ;  d,  layer  of  large  follicles  ; 
e,  zona  vasculosa 


Female  Gexital  Organs.  ^87 


O" 


The  stroma  of  this  latter,  however,  is  made  up 
of  bundles  of  shorter  or  longer  transparent  spindle- 
shaped  cells,  each  with  an  oval  nucleus.  These 
bundles  of  spindle-shaped  cells  form,  by  crossing 
and  interlacing,  a  tolerably  dense  tissue,  in  which 
lie  embedded  in  special  distribution  the  Graafian 
follicles.  Around  the  lai-ger  examples  of  the  latter 
the  spindle  shaped  cells  form  more  or  less  con- 
centric layers.  In  the  human  ovary  bundles  of 
librous  tissue  are  also  met  with. 

The  spindle-shaped  cells  are  most  probably  a 
young  state  of  connective  tissue. 

Between  these  bundles  of  spindle-shaped  cells 
occur  cylindrical  or  irregular  streaks  or  groups  of 
polyhedral  cells,  each  with  a  spherical  nucleus  ;  they 
correspond  to  the  interstitial  epithelial  cells  men- 
tioned in  the  testis,  and  they  are  also  derived  from 
the  fcetal  Wolffian  body. 

344.  According  to  the  distribution  of  the  Graafian 
follicles,  the  following  layers  can  be  distinguished  in 
the  ovary  : — 

{a)  The  albuginea.  This  is  the  most  peripheral 
layer  not  containing  any  Graafian  follicles.  It  is 
composed  of  the  bundles  of  spindle-shaped  cells,  in- 
timately interwoven.  In  man,  an  outer  and  inner 
longitudinal,  and  a  middle  circular,  layer  can  be  made 
out  (Henle).  In  some  mammals  an  otiter  longi- 
tudinal, an  inner  circidar,  or  slightly  oblique  layer 
can  be  distinguished  in  the  albu2:inea. 

The  free  surface  of  the  albuginea  is  covered  with 
a  single  layer  of  polyhedral,  or  short  columnar 
granular-looking  epithelial  cells,  the  germinal 
epithelium  (Waldeyer).  This  epithelium,  in  its 
shape  and  aspect,  forms  a  marked  contrast  to  the 
transparent,  flattened,  endothelial  plates  covering 
the  ligamentum  latum. 

345.  [h)  TJie  cortical  layer  (Schron). — This  is   a 


;88 


Elements  of  Histology 


% 


mBmmm 


layer  containing  the  smallest  Graafian  follicles,  either 
aggregated  as  a  more  or  less  continuous  layer  (cat  and 
rabbit),  or  in  small  groups  (human),  separated  by  the 
stroma.  These  follicles  are  spherical  or  slightly  oval, 
of  about  Y-u\,o  inch  in  diameter,  and  each  of  them  is 
limited  by  a  delicate  raemhrana  propria.  Inside  of 
this  is  a  layer  of  flattened,  trans- 
parent, epithelial  cells,  each  with  an 
oval,  flattened  nucleus ;  this  is  the 
membrana  granulosa.  The  'space 
within  the  follicle  is  occupied  by, 
and  filled  up  with,  a  spherical  cell — 
the  ovum  cell,  or  ovum.  This  is 
composed  of  a  granular-looking  pro- 
toplasm, and  in  this  is  a  big  spherical, 
or  slightly  oval,  nucleus — the  germinal 
vesicle.  The  substance  of  this  is  either 
a  fine  reticulum,  limited  by  a  delicate 
membrane,  with  one  or  more  nucleoli 
or  germinal  spots,  or  it  is  in  one  of 
the  phases  of  indirect  division  or 
karyomitosis,  thus  indicating  division 
of  the  ovum. 

346.    (c)  From  this  cortical  layer  to 

the  zona  vasculosa  we  find  embedded 

the  stroma  isolated  Graafian  follicles  of  various 

increasino-   from     the    former    to    the    latter. 


Fig.  247.— A  small 
Graafian  Follicle, 
from  the  Ovary  of 
Cat.     {Atlas.) 

The  follicle  is  lined 
with  a  layer  of 
colunmar  epithe- 
lial cells  —  the 
lueinbrana  granu- 
losa. The  ovum 
fills  out  the  cavity 
of  the  follicle;  it 
is  surrounded  by 
a  thin  zona  pellu- 
cida,  and  it  in- 
cludes a  germinal 
vesicle  or  nucleus 
with  the  intra- 
nuclear reticulum. 


m 

sizes 


The 


1 

2  0 


biggest    follicles    measure    in    diameter    about 
Those    of  the    middle  laj^ers    are   of  me- 


inch 


In  them  we  find  inside 
the  membrana  granulosa, 
layer  of  transparent,  co- 
The  ovum,  larger  than  in 
the  small  cortical  follicles,  fills  out  the  cavity  of  the 
follicle,  and  is  limited  by  a  thin  hyaline  cuticle — the 
zona  peUncida.  This  appears  as  an  excretion  of  the 
cells  of  the  membrana  granulosa.     The  protoplasm  of 


dium    size    (Fig.    247). 
the    membrana    propria 
made     up     of    a    single 
lumnar,   epithelial  cells. 


Female  GEyiTAL  Organs. 


3S9 


tlie  OMiiii  is  tibrillateil.  The  part  siuTOunding  the 
germinal  vesicle  is  more  ti-auspaient,  and  stains 
ditlerently  in  osniic  acid  than  the  peripheral  part. 
The  big  nucleus,  or  germinal  vesicle,  is  limited  by  a 
distinct  membrane,  and  inside  this  meml^rane  is  a 
reticulum  ^vith 
generally  one 
big  nucleolus 
or    germinal 

0J)Ot. 

Between 
these  medium- 
sized  follicles 
and  the  small 
follicles  of  the 
cortical  layer 
we  lind  all  in- 
termediate de- 
grees as  regards 
size  of  the  fol- 
licle and  the 
ovum,  and  es- 
pecially as  re- 
gards the  shape 
of  the  cells  of 
the  merabrana 
granulosa,  the 
intermediate  sizes  of  follicles  being  lined  by  a  granu- 
losa made  up  of  a  layer  of  polyhedi-al  epithelial 
cells. 

347.  The  deeper  Graafian  follicles — i.e.  those 
that  are  to  be  regarded  as  big  follicles — contain  an 
o\um,  occasionally  two  or  even  three  ova,  which  is 
similar  to  that  of  the  previous  follicles,  except  that  it 
is  larger,  and  its  zona  pellucida  thicker.  The  ovum 
does  not  fill  out  the  whole  ca^-ity  of  the  follicle,  since 
at  one  side,  between  it  and  the  membrana  granulosa, 


Fii:.  248.— Large  Graafian  Follicle  of  the  Ovan"  ot 
Cat. 

The  follicle  is  limited  by  a  capsule. the  thecafolliculi ; 
tlie  lueiubraDa  granulosa  is  composed  of  several 
layers  of  epithtlial  cells.  The  ovum  with  its  distinct 
1) valine  zona  pellucida  is  emliedded  in  the  epithelial 
cells  of  the  discus  proligerus.  The  cavity  of  the 
follicle  is  filled  with  fluid,  the  liciuor  foUiculi. 


390  Elements  of  Histology. 

there    is    an  albuminous   riuid,   tljc    ludiment  of    the 
liquor  folliciili, 

348.  The  largest  or  most  advanced  follicles  are  of 
great  size,  easily  visible  by  the  naked  eye,  and  con- 
tain a  large  quantity  of  this  liquor  folliculi  (Fig.  248). 
In  fact,  the  ovum  occupies  only  a  small  part  of  the 
cavity  of  the  follicle.  The  ovum  is  big,  surrounded 
by  a  thick  zona  pellucida,  is  situated  at  one  side,  sur- 
rounded by  the  discus  proligerus.  This  consists  of 
layers  of  polyhedral  cells,  except  the  cells  immediately 
around  the  zona  pellucida,  which  are  columnar.  The 
ovum  with  its  discus  proligerus  is  connected  with  the 
membrana  granulosa.  This  latter  consists  of  stratified 
pavement  epithelium,  forming  the  entire  lining  of  the 
follicle.  The  outermost  layer  of  cells  is  columnar. 
The  membrana  propria  of  these  big  follicles  is 
strenothened  bv  concentric  lavers  of  the  stroma 
cells,  and  this  represents  the  tunica  fibrosa  (Henle) 
or  outer  coat  of  the  follicle — theca  folliculi  externa. 
Xumerous  blood  capillaries  connected  into  a  network 
surround  the  big  follicles. 

In  those  follicles  that  contain  a  greater  or  smaller 
amount  of  the  liquor  folliculi  we  notice  in  the  fluid  a 
variable  number  of  detached  granulosa  cells  in  various 
stages  of  vacuolation,  maceration,  and  disintegration. 

349.  In  connection  with  the  medium-sized  and 
large  Graafian  follicles  are  seen  occasionally  smaller 
or  larger  solid  cylindrical  or  irregularly-shaped  out- 
oTowths  of  the  membrana  o'ranulosa  and  membrana 
propria ;  they  indicate  a  new  formation  of  Graafian 
follicles,  some  containing  a  new  ovum.  When  these 
side  branches  become  by  active  growth  converted  into 
larger  follicles,  they  may  remain  in  continuity  with 
the  parent  follicle,  or  may  be  constricted  off  alto- 
gether. In  the  first  case,  we  have  one  large  follicle 
w^itli  two  or  three  ova,  according  as  a  parent  follicle 
Itg-s  given  origin  to  one  or  two  new  outgrowths. 


Female  Genital  Organs.  391 

Amongst  the  epithelial  cells  constituting  the 
stratified  niembrana  granulosa  of  the  ripe  follicles 
we  notice  a  nucleated  reticulum. 

Many  follicles  reach  ripeness,  as  far  as  size  and 
constituent  elements  are  concerned,  long  before 
puberty,  and  they  are  subject  to  degeneration  ;  but 
this  process  of  degeneration  involves  also  follicles  of 
smaller  sizes. 

350.  Before  menstruation,  generally  one,  occasion- 
ally two  or  more  of  the  ripe  follicles  become  very 
hyperh?emic.  They  grow,  in  consequence,  very  rapidly 
in  size  ;  their  liquor  folliculi  increases  to  such  a  degree 
that  they  reach  the  surface  of  the  ovary  ;  finally — 
i.e.  during  menstruation — they  burst  at  a  superficial 
point ;  the  ovum,  with  its  discus  proligerus,  is  ejected, 
and  brought  into  the  abdominal  ostium  of  the  oviduct. 
The  cavity  of  the  follicle  collapses,  and  a  certain 
amount  of  l)lood,  derived  from  the  broken  capillaries 
of  the  wall  of  the  follicle,  is  effused  into  it.  The 
follicle  is  converted  into  a  corpus  luteum  by  an  active 
multiplication  of  the  cells  of  the  granulosa.  New 
capillaries  with  connective-tissue  cells  derived  from 
the  theca  folliculi  externa  gradually  grow  into  the 
interior — i.e.  between  the  cells  of  the  granulosa.  This 
growth  gradually  fills  the  follicle,  except  the  centre ; 
this  contains  blood  pigment  in  the  shape  of  granules, 
chiefly  contained  in  large  cells,  and  a  few  new  blood- 
vessels,^tlie  blood  pigment  being  the  remains  of  the 
original  blood  eflused  into  the  follicle.  But,  ulti- 
mately,  all  the  pigment  disappears,  and  a  sort  of 
gelatinous  tissue  occupies  the  centre,  while  the  peri- 
phery— i.e.  the  greater  part  of  the  follicle — is  made 
up  of  the  hypertrophied  granulosa,  with  young  capil- 
lary vessels  between  its  cells.  The  granulosa  cells 
undergo  fatty  degeneration,  becoming  filled  with 
several  small  fat  globules,  which  gradually  become 
confluent  into  a  big  globule.      In  this  state  the  corpus 


392  Elements  of  Histology. 

luteum  is  complete,  and  has  reached  the  height  of  its 
progressive  growth.  The  tissue  is  then  gradually 
al)Sorbed,  and  cicatricial  tissue  is  left.  When  this 
shrinks  it  produces  a  shrinking  of  the  corpus  luteum. 
This  represents  the  last  stage  in  the  life  of  a  Graafian 
follicle.  The  corpus  luteum  of  Graafian  follicles,  of 
which  the  ovum  has  been  impregnated,  grows  to  a 
much  larger  size  than  under  other  conditions,  the 
granulosa  becoming  by  overgrowtli  much  folded. 

351.  Development  of  tlie  ovary  and  Oraa- 
Han  follicles.— The  germinal  epithelium  of  the  sur- 
face of  the  foetal  ovary  at  an  early  stage  undergoes 
rapid  multiplication,  in  consequence  of  which  the  epi- 
thelium becomes  greatly  thickened.  The  vascular 
stroma  of  the  ovary  at  the  same  time  increases,  and 
permeates  the  thickened  germinal  epithelium.  The 
two  tissues,  in  fact,  undergo  mutual  ingrowth,  as  is  the 
case  in  the  development  of  all  glands — namely,  the 
epithelial  or  glandular  part  sutlers  mutual  ingrowth 
with  the  vascular  connective- tissue  stroma. 

In  the  case  of  the  ovary,  larger  and  smaller 
islands  or  nests  (Balfour)  of  epithelial  cells  are  thus 
gradually  diflferentiated  ofi'  from  the  superficial  epi- 
thelium. These  nests  are  largest  in  the  depth  and 
smallest  near  the  surface.  They  remain  in  connec- 
tion with  one  another  and  with  the  surface  for  a 
considerable  period.  Even  some  time  after  birth 
some  of  the  superficial  nests  are  still  connected  with 
the  surface  epithelium,  and  with  one  another  (Fig. 
249).  These  correspond  to  the  ovarial  tubes  (Pfiiiger). 
While  in  the  rabbit  these  nests  are  solid  collections, 
in  the  dog  they  soon  assume  the  character  of  tubular 
structures  (Pfiiiger,  Schafer).  The  cells  constituting 
the  nests  undergo  multi})lication  (by  karyomitosis), 
in  consequence  of  which  the  nests  increase  in  size, 
and  even  new  nests  may  be  constricted  off  from  old 
ones  {see  also  above). 


Female  Genital  Organs. 


193 


3.")2,  At  the  earliest  stages  we  notice  in  the 
germinal  epithelium  some  of  the  cells  becoming  en- 
larged in  their  cell  body,  and  especially  their  nucleus  : 
these  represent  the  primitive  ova.  AVhen  the  ger- 
minal epithelium  undergoes  the  thickening  above  men- 
tioned, and  when  this  thickened  epithelium  separates 


Fig.  240. — From  a  Vertical  Section  tlirough  Ovary  of  a  Xewly-borji  Child. 
{Wo.ldeyer,  in  Strieker's  Manual.) 

a,  Germinal  epithelium ;  6,  ovarian  tube  ;  c.  primitive  ova  ;  d,  longer  tubes  be- 
coming consiricted  off  into  several  Graafian  follicles;  e,  large  nests;  /, 
iso'ated  finished  Graafian  follicles ;  ^,  blood-vessels. 

into  the  nests  and  ovarial  tubes,  there  is  a  continued 
formation  of  primitive  ova  —  i.e.  cells  of  the  nests 
undergo  the  enlargement  of  cell-body  and  nucleus 
by  which  they  are  converted  into  primitive  ova. 
Like  the  other  epithelial  cells,  tlie  primitive  ova 
of  the  nests  and  ovarial  tubes  undergo  division  into 
two    or    even    more    primitive    ova    after    the    mode 


394  Elements  of  Histology. 

of  karyomitosis  (Balfour).     Thus  each  nest  contains 
a  series  of  ova. 

353.  The  ordinary  small  epithelial  cells  of  the 
nests  and  ovarial  tubes  serve  to  form  the  membrana 
granulosa  of  the  Graafian  follicles.  According  to  the 
number  of  ova  in  a  nest  or  in  an  ovarial  tube,  a  sub- 
division takes  place  in  so  many  Graafian  follicles, 
each  consisting  of  one  ovum  with  a  more  or  less 
complete  investment  of  small  epithelial  cells — i.e.  a 
membrana  granulosa.  This  subdivision  is  brought 
about  by  the  ingrowth  of  the  stroma  into  the  nests. 

The  superficial  nests  being  the  smallest,  as  above 
stated,  form  the  cortical  layer  of  the  small  Graafian 
follicles  ;  the  deeper  ones  give  origin  to  larger  follicles. 
Thus  we  see  that  the  ovum  and  the  cells  of  the 
membrana  granulosa  are  derived  from  the  primary 
germinal  epithelium ;  all  other  parts — membrana 
})ropria,  theca  externa,  stroma,  and  vessels — are  de- 
rived from  the  foetal  stroma. 

There  is  a  ofood  deal  of  evidence  to  show  that  ova 
and  Graafian  follicles  are,  as  a  rule,  reproduced  after 
birth  (Pfliiger,  Kolliker),  although  other  observers 
(Bischofi",  Waldeyer)  hold  the  opposite  Adew. 

3.54.  (2)  Till'  oviduct. — The  o\nduct  consists  of 
a  lining  epithelium,  a  mucous  membrane,  a  muscular 
coat,  and  an  outer  fibrous  coat — the  serous  covering, 
or  peritoneum.  The  epithelium  is  columnar  and 
ciliated.  The  mucous  membrane  is  much  folded  ;  it 
is  a  connective-tissue  membrane  with  networks  of 
capillary  blood  vessels.  In  man  and  mammals  there 
are  no  proper  glands  present,  although  there  are  seen 
appearances  in  sections  which  seem  to  indicate  the 
existence  of  short  gland  tubes ;  but  these  appear- 
ances are  explained  by  the  folds  of  the  mucous 
membrane.  The  muscular  coat  is  composed  of  non- 
striped  muscular  tissue  of  a  pre-eminently  circular 
arrangement  \    in    the   outer    part    there    are    a    few 


Female  Gexital   Orgaxs.  395 

oblique  aiul  longitudinal  bundles.  The  serous  cover- 
ing contains  numerous  elastic  tii)ril~^  in  a  connective- 
tissue  matrix. 

355.  (3)  The  uterus. — The  epithelium  lining 
the  cavity  of  the  uterus  is  a  single  la^'er  of  columnar 
cells,  each  with  a  l)undle  of  cilia  on  their  free  sur- 
face. These  are  very  easily  detached,  and  therefore 
difficult  to  tind  in  a  hardened  and  preserved  specimen. 
But  in  the  fresh  and  well-preserved  human  uterus 
(Friedlander),  as  well  as  in  that  of  mammals,  the 
cells  are  distinctly  ciliated.  The  whole  canal  of  the 
cervix  is  in  the  adult  lined  with  ciliated  epithelium, 
but  in  children,  according  to  Lott,  only  in  tlie  upper 
half.  The  surface  of  the  portio  vaginalis  uteri  is, 
like  that  of  the  vagina,  covered  with  stratitied  pave- 
ment epithelium. 

356.  The  mucous  membrane  of  the  cervix  is 
diflerent  from  that  of  the  fundus.  In  the  former 
it  is  a  fibrous  tissue  possessed  of  permanent  folds — 
the  palma?  plicatoe.  Few  thin  bundles  of  non-striped 
muscular  tissue  penetrate  into  these  from  the  outer 
muscular  coat.  Between  the  palma?  plicata?  are  the 
openings  of  minute  gland-tubes,  more  or  less  cylin- 
drical in  shape.  They  possess  a  membrana  propria 
and  a  distinct  lumen  lined  with  a  single  layer  of 
columnar  epithelial  cells,  which,  according  to  some 
observers,  are  ciliated  in  the  newly-born  child,  but, 
according  to  Friedlander,  are  alwavs  non-ciliated. 
Goblet  cells  are  met  with  amongst  the  lining  e^rti- 
thelium.  Several  observers  (Kolliker,  Hennig,  Tyler 
Smith,  and  others)  maintain  the  existence  of  minute, 
thin,  and  long  vascular  papilhe  projecting  above  the 
general  surface  of  the  mucous  membrane  in  the  lower 
})art  of  the  cervix ;  these  apparent  papilla?  are,  how- 
ever, only  due  to  sections  through  the  folds  of  the 
mucous  membrane.  The  mucous  membrane  of  the 
fundus  is  a  spongy  plexus  of  tine  bundles  of  fibrous 


396  Elements  of  Histology. 

tissue,  covered  or  lined  respectively  with  numerous 
small  endothelial  plates,  each  with  an  oval  flattened 
nucleus.  The  spaces  of  this  spongy  substance  are 
lymph  spaces,  and  contain  the  glands  and  the  blood- 
vessels (Leopold). 

357.  The  glands  —  glaiKliilii'  iitei'iiiSB  —  are 
short  tubular  glands  lodged  in  the  mucous  mem- 
brane and  opening  into  the  uterine  cavity.  During 
puberty  their  number  and  their  size  increase  con- 
siderably, new  glands  being  formed  by  the  ingrowth 
of  the  surface  epithelium  into  the  mucous  membrane 
(Kundrat  and  Engelmann).  During  menstruation, 
and  especially  during  pregnancy,  they  greatly  increase 
in  length.  They  are  more  or  less  wavy  and  branched 
at  the  bottom.  A  delicate  membrana  propria  forms 
the  boundary  of  the  tube ;  a  distinct  lumen  is  seen 
in  the  middle,  and  this  is  lined  with  a  single  layer 
of  ciliated  columnar  epithelium  (Allen  Tliomson, 
Nylander,  Friedliinder,  and  others). 

358.  Durino-  menstruation  the  thickness  of  the 
mucous  membrane  increases,  the  epithelium  of  the 
surface  and  of  the  greater  part  of  the  glands  being 
destroyed  by  fatty  degeneration,  and  linally  altogether 
detached.  Afterwards  its  restitution  takes  place  from 
the  remnant  in  the  depth  of  the  glands.  But  accord- 
ing to  J.  Williams  and  also  Wyder,  the  greater  part 
of  the  mucous  membrane,  in  addition  to  the  epithe- 
lium, is  destroyed  during  menstruation. 

The  muscular  coat  forms  the  thickest  part  of  the 
wall  of  the  uterus  ;  it  is  composed  entirely  of  the  non- 
striped  variety. 

In  the  cornua  uteri  of  mammals  the  muscular 
coat  is  generally  composed  of  an  inner  thicker  circular 
and  an  outer  thinner  longitudinal  stratum,  a  few 
oblique  bundles  passing  from  the  latter  into  the 
former.  In  the  human  uterus  the  muscular  coat  is 
composed  of  an  outer  thin  longitudinal,  a  middle  thick 


FiiMAr.E  Gkxital   Okgaxs.  397 

layer  of  ciivular  bundles,  and  an  inner  thick  one  of 
oblique  and  circular  bundles.  Within  these  layers 
the  bundles  form  plexuses. 

359.  The  arterioles  in  the  cervix  and  their 
capillaries  are  distinguislied  by  the  great  thickness  of 
their  wall.  The  mucous  membrane  contains  the 
capillari/  netioorks.  These  discharge  their  blood  into 
veins  situated  in  the  muscular  coat.  Here  the  veins 
are  very  numerous  and  arranged  in  dense  j^lexuses, 
those  of  the  outer  and  inner  stratum  beinof  smaller 
than  those  of  the  middle  stratum,  where  thev  corre- 
spond to  huge  irregular  sinuses,  the  bundles  of 
muscular  tissue  of  the  muscular  coat  giving  special 
support  to  these  sinuses.  Hence  the  plexus  of  venous 
sinuses  of  the  middle  stratum  represents  a  sort  of 
cavernous  tissue. 

360.  The  lympliaties  are  very  numerous  ;  in 
the  connective  tissue  of  the  muscular  coat  are  lymph 
sinuses  and  lymph  clefts  forming  an  intercommuni- 
cating system  ;  they  take  up  the  lymph  sinuses  of  the 
mucous  membrane  above  mentioned,  and  on  the  other 
hand  lead  into  a  plexus  of  efferent  lymphatic  vessels 
with  valves,  situated  in  the  subserous  connective  tissue. 

The  nerves  entering  the  mucous  membrane  are 
connected  with  ganglia.  According  to  Lindgren, 
there  is  in  the  mucous  membrane  a  plexus  of  non- 
medullated  nerve  fibres  which,  near  the  epithelium, 
break  up  into  their  constituent  primitive  fibrill^. 

361.  (4)  Tlie  vag-iiia — The  epithelium  lining 
the  mucous  membrane  is  a  thick,  stratified  pavement 
epithelium.  The  superficial  part  of  the  mucous  mem- 
brane— i.e.  the  mucosa — is  a  dense,  fibrous  connective 
tissue  with  numerous  networks  of  elastic  fibres  ;  it 
projects  into  the  epithelium  in  the  shape  of  numerous 
long,  simple  or  compound  papillae,  each  with  a  single 
or  complex  loop  of  capillary  blood-vessels.  The 
mucosa  with  the  covering  epithelium  projects  above 


398  Elements  of  Histology. 

the  general  surface  in  the  shape  of  longer  or  shorter, 
conical  or  irregular,  pointed  or  blunt,  permanent 
folds — the  rugse.  These  contain  a  plexus  of  large 
veins,  between  which  are  bundles  of  non-striped 
muscular  tissue ;  hence  they  resemble  a  sort  of 
cavernous  tissue. 

Outside  of  the  mucosa  is  the  loose  submucosa, 
containing  a  second  venous  plexus  ;  its  meshes  are 
elongated  and  parallel  to  the  long  axis  of  the  vagina. 
Outside  of  the  submucous  tissue  is  the  muscular  coat, 
consisting  of  an  inner  circular  and  an  outer  longitu- 
dinal stratum  of  non-striped  muscular  tissue.  Oblique 
bundles  pass  from  one  stratum  into  the  other.  From 
the  circular  stratum  bundles  may  l^e  traced  into  the 
submucosa  and  mucosa.  A  layer  of  fibrous  tissue 
forms  the  outer  boundary  of  the  wall  of  the  vagina, 
and  in  it  is  the  most  conspicuous  plexus  of  veins,  the 
plexus  venosus  vaginalis.  This  plexus  also  contains 
Wndles  of  non-striped  muscular  tissue,  and  therefore 
resembles  a  cavernous  tissue  (Gussenbaur).  It  is 
not  quite  definitely  ascertained  whether  or  not  there 
are  secreting  glands  in  the  mucous  membrane  of  the 
vagina.  Yon  Preuschen  and  also  Hennig  described 
tubular  glands  in  the  upper  part  of  the  fornix  and  in 
the  introitus  vagina?. 

The  lymphatics  form  plexuses  in  the  mucosa,  sub- 
mucosa, and  the  muscular  coat.  The  first  are  small 
vessels,  the  second  are  larger  than  the  third  and 
possess  valves.  The  efferent  vessels  form  a  rich 
plexus  of  large  trunks  with  saccular  dilatations  in 
the  outer  fibrous  coat. 

'J'here  are  in  the  mucous  membrane  solitary  lymph 
follicles  and  difi'use  adenoid  tissue  (Loevenstein). 

Numerous  ganglia  are  contained  in  the  nerve 
plexus  belonging  to  the  muscular  coat. 

End  bulbs  in  connection  with  the  nerve  fibres  of 
the  mucosa  have  been  mentioned  in  Chapter  XV. 


Female  Genital   Organs.  399 

362.  (5)  TIk'  iirrllira.  -^The  structure  of  the 
female  urethra  is  siinihir  to  that  of  the  male,  except 
that  the  lining  epithelium  is  a  sort  of  stratified 
transitional  epithelium,  the  superficial  cells  being 
short,  columnar,  or  club-shaped  ;  underneath  this  layer 
are  several  layers  of  polyhedral,  or  cubical  cells. 
Near  the  orificium  externum  the  epithelium  is 
stratified  ]3avenient  epithelium. 

The  muscular  coat  is  composed  of  an  inner  longi- 
tudinal, and  an  outer  circular,  layer  of  non-striped 
muscular  tissue. 

363.  (6)  Tlie  iiyiiiplise,  clitorif^,  aii<l  vcsti- 
biiliiiii. — These  are  lined  with  thick  stratified  epi- 
thelium ;  underneath  is  a  fibrous  connective-tissue 
mucous  membrane,  extending  into  the  epithelium  in 
the  shape  of  C3^1indrical  pajjill^e  with  capillary  loops 
and  nerve  endings  (end  bulbs).  The  nympha^  contain 
large  sebaceous  follicles,  but  no  hairs. 

The  nymphse  contain  a  plexus  of  large  veins  with 
bundles  of  non-striped  muscular  tissue ;  hence  it 
resembles  a  cavernous  tissue  (Gussenbaur).  The 
corpora  cavernosa  of  the  clitoris,  the  glans  clitoridis, 
and  the  bulbi  vestibuli,  corresjjond  to  the  analogous 
parts  in  the  penis  of  the  male.  The  glands  of 
Bartholin  correspond  in  structure  to  the  glands  of 
(Jowper  in  the  male. 


400 


CHAPTER    XXXV. 

THE       MAM  M  A  R  Y       r;  L  A  X  D  . 

364.  This,  like  other  glands,  consists  of  a  frame- 
work and  parenchyma.  The  former  is  lamellar  fibrous 
connective  tissue  subdividing  the  latter  into  lobes  and 
lobules  and  containing  a  certain  amount  of  elastic 
fibres.  In  some  animals  (rabbit,  guinea-pig)  there  are 
also  small  bundles  of  non-striped  muscular  tissue. 
From  the  interlobular  septa  tine  bundles  of  fibrous 
tissue  with  branched  connective-tissue  corpuscles  pass 
between  the  alveoli  of  the  gland  substance.  The 
amount  of  this  interalveolar  tissue  varies  in  difterent 
places,  l3ut  in  the  active  gland  is  always  relatively 
scanty. 

Migratory  or  lymph  corpuscles  are  to  be  met  with 
in  the  interalveolar  connective  tissue  of  both  active 
and  resting  glands.  In  the  latter  they  are  more 
numerous  than  in  the  former.  According  to  Creighton, 
they  are  derived,  in  the  resting  gland,  from  the  epi- 
thelium of  the  o'land  alveoli.  Granular  large  vellow 
(pigmented)  nucleated  cells  occur  in  the  connect! v% 
tissue,  and  also  in  the  alveoli  of  the  resting' 
o^land,  and  Creio:hton  considers  them  both  identical, 
and  derived  from  the  alveolar  epithelium.  And 
according  to  this  author,  the  production  of  these  cells 
would  constitute  the  principal  function  of  the  resting 
gland. 

The  large  ducts  as  they  pass  from  the  gland  to  the 
nipple  acquire  a  thick  sheath,  containing  bundles 
of    non-striped    muscular    tissue.       These   latter   are 


jlfA MM.l K  ) '    GlANP. 


401 


derived  from  tlie  bundles  of  non-striped  muscular 
tissue  present  in  the  skin  of  the  nipple  of  the  ])re;ist. 

The  small  ducts  in  the  lolniles  of  the  gland  tissue 
possess  a  membrana  propria,  and  a  lining — a  single 
layer  of  longer  or  shorter  columnar  epithelial  cells. 

The    terminal    branches    of    the    ducts — i.e.     just 


Fig.  2oO.— From  a  Section  through  the  JIamniary  Gland  of  Cat  in  a  late 
stage  of  pregnancy.     {Atlas.) 

a.  Epithelial  cells  lining  tlie  gland-alvedli,  seen  iu  profile;  b,  the  same,  seen 
from  the  surface.  Many  epithelial  cells  coutiiiu  an  oil  globule.  In  the  cavity 
of  some  of  the  alveoli  are  milk  globules  and  granular  matter. 


before  these  latter  pass  into  the  alveoli — are  lined  ^vith 
a  single  layer  of  flattened  pavement  epithelium  cells  ; 
they  are  analogous  to  the  intermediate  portion  of  the 
ducts  of  the  salivary  glands  [see  Chap.  XXIII.). 

365.   Each  of  these  terminal  branches  divides  and 

takes  up  several  alveoli  (Fig.   250).      These  are  wavy 

tubes,    saccular   or    flask-shaped.        The    alveoli    are 

larger  in  diameter  than  the  intralobular  ducts.     Each 

A  A 


40  2  Elements  of  Histology. 

alveolus  in  tlie  active  gland  has  a  relatively  large 
cavity,  varying  in  different  alveoli ;  it  is  lined  with  a 
single  layer  of  polyhedral,  granular-looking,  or  short 
columnar  epithelial  cells,  each  with  a  spherical  nucleus  ; 
a  membrana  propria  forms  the  outer  limit.  This 
membrana  propria,  like  that  of  the  salivar}^,  lachrymal 
and  other  glands,  is  a  basket-work  of  branched  cells. 

In  the  active  gland  each  epithelial  cell  is  capable 
of  forming  in  its  interior  one  or  more  smaller  or  larger 
oil  globules.  These  may,  and  generally  do,  become 
confluent,  and,  pressing  the  nucleus  towards  one  side 
of  the  cell,  give  to  the  latter  the  resemblance  of  a  fat- 
cell.  The  oil  globules  linally  pass  out  from  the  cell 
protoplasm  into  the  lumen  of  the  alveolus,  and 
represent  now  the  milk  globules.  The  cell  resumes  its 
former  solid  character,  and  commences  again  to  form 
oil  globules  in  its  protoplasm.  The  epithelial  cells, 
as  long  as  the  secretion  of  milk  lasts,  go  on  again  and 
aerain  forming:  oil  orlobules  in  the  above  manner 
without  being  themselves  destroyed  (Langer).  The 
milk  globules,  when  in  the  lumen  of  the  alveoli,  are 
enveloped  in  a  delicate  cuticle — the  albumin  mem- 
brane of  Ascherson,  which  they  receive  from  the  cell 
protoplasm. 

According  to  the  state  of  secretion,  most  epithelial 
cells  lining  an  alveolus  may  be  in  the  condition  of 
forming  oil  globules,  or  only  some  of  them  ;  and 
according  to  the  rate  in  which  milk  globules  are 
formed  and  carried  away,  the  alveoli  differ  in  the 
number  of  milk  globules  they  contain. 

According  to  Schmid,  the  epithelial  cells,  after 
having  secreted  milk  globules  for  some  time,  finally 
break  up,  and  are  replaced  by  new  epithelial  cells 
derived  by  the  division  of  the  other  still  active 
epithelial  cells. 

366.  The  resting  gland — i.e.  the  gland  of  a  non-preg- 
nant or  non-suckling  individual — contains,  compara- 


Ma.umakv  Gland.  403 

tivfly  sj»eal<iii,i,%  few  alveuli,  but  a  great  <leal  of  tilnous 
connective  tissue  ;  the  alveoli  are  all  solid  cylinders, 
containing  within  the  limiting  nieinbrana  propria 
masses  of  polyliedral  granular  looking  epithelial  cells. 
During  pregnancy  these  solid  cylinders  undergo  mul- 
tiplication, elongation,  and  thickening,  owing  to  the 
rapid  division  of  the  constituent  epithelial  cells. 

Finally,  when  milk  secretion  commences,  the  cells 
occupying  the  central  part  of  the  alveolus  undergo  the 
fatty  degeneration  just  like  the  peripheral  cells,  but 
they — i.e.  the  central  cells — are  eliminated,  while  the 
peripheral  ones  remain.  The  central  cells  are  the 
cohstrum  corpj'.sries,  and  consequently  they  are  found 
in  the  milk  of  the  first  few  days  only. 

3G7.  Ordinary  milk  contains  no  colostrum  corpus- 
cles, ])ut  only  milk  globules  of  many  various  sizes,  from 
the  size  of  a  granule  to  that  of  a  globule  several  times 
as  big  as  an  epithelial  cell  of  an  alveolus  of  the  milk 
gland.  These  large  drops  are  produced  by  fusion  of 
small  globules  after  having  passed  out  of  the  alveoli. 
Each  milk  globule  is  an  oil  globule  surrounded,  as 
stated  above,  by  a  thin  albuminous  envelope — Ascher- 
son's  membrane.  The  small  bits  of  granular  substance 
met  with  here  and  there  are  probably  the  remains  of 
broken-down  protoplasm  of  epithelial  cells, 

3G8.  Each  gland  alveolus  is  surrounded  V^y  a  dense 
network  of'  capWarij  Wood-vessels.  The  alveoli  are 
surrounded  by  hjmpJi  spaces  like  those  in  the  salivary 
glands  (Covne),  and  these  spaces  lead  into  aetiKorks  of 
hjiiii)lifdic  vessels  of  the  interlobular  connective  tissue. 


404 


CHAPTER    XXXVI. 

THK     SKIN. 

369.  The  skin  consists  of  the  following  layers 
(Fig.  252)  : — (1)  The  epidermis;  (2)  the  corium,  or 
cutis  vera,  with  the  papilla? :  (3)  the  subcutaneous 
tissue,  with  the  adipose  layer  or  the  adipose  tissue, 

370.  (1)  The  epidermis  (Fig.  25),  in  all  its 
constituent  elements,  has  been  minutely  described  in 
Chapter  III.  Its  thickness  varies  in  different  parts, 
and  is  chiefly  dependent  on  the  variable  thickness  of 
tlie  stratum  corneum.  This  is  of  great  thickness  in 
the  palm  of  the  hand  and  the  sole  of  the  foot.  The 
stratum  Malpigliii  fits  into  the  depressions  between 
the  papilla?  of  the  corium  as  the  interpapillary  pro- 
cesses. The  i^resence  of  prickle  cells,  of  pigment 
granules,  and  of  branched  interstitial  nucleated  cells, 
etc.,  has  been  mentioned  in  Chapter  III. 

There  occur  in  the  stratum  ]Malj)ighii  migrator}- 
cells  of  granular  aspect ;  they  appear  to  migrate  from 
the  papillary  layer  of  the  corium  into  the  stratum 
IMalpighii  (Biesiadecki). 

In  the  coloured  skin — p.g.  of  the  negro — pigment 
granules  are  abundant  in  the  cell  substance  of  the 
stratum  Malpigliii,  especially  in  the  deeper  layers  ; 
but  there  is  present  an  almost  continuous  layer  of 
pigment  in  the  superficial  layers  of  the  stratum 
corneum  (Fig.  251). 

371.  (2)  The  coriiiiii  is  a  dense  feltwork  of 
bundles  of  fibrous  connective  tissue,  w^ith  a  large 
admixture  of  networks  of  elastic  fibres.      From  the 


Sa'/iv. 


405 


surface  of  the  coriuui  project  small  conical  or  cylin- 
drical papilla'..  These  are  best  developed  in  those 
parts  where  the  skin  is  thick — e.g.  volar  side  of 
hand  and  foot,  scalp,  lips   of  mouthy  etc.     Between 


Fig,  261. — From  Vertical  Section  througli  Epidermis  of  Skin  of  Finger  of 
Negro.     (Photo.     Moderate  magnification.) 

a,  Surface  of  stratum  corneura,  much  pijjiuented;  ft,  stratum  corneum ;  e, 
stratum  Maliiighii,  containing  pigment  ni  its  cells;  (?,  corinm  with  papilhe 
extending  into  the  stratum  Malpigliii. 


the  surface  of  the  coriuni  and  the  epidermis  there 
is  a  basement  membrane.  Migratory  cells,  with  and 
without  pigment  granules  in  their  interior,  are  met 
with,  especially  in  the  superficial  part  of  the  corium ; 
they,  as  well  as  the  fixed  or  branched  connective- 
tissue  corpuscles  (see  par.  40),  and  other  structures,  as 
vessels  and  nerves,  lie  in  the  interfascicular  spaces. 


4o6 


Elements  of  Histology. 


372.  (3)  The  supei^cial  part  of  the  subcuta- 
iieoii«»  tissue  insensibly  merges  into  the  deep  part  of 
the  corium  ;  it  cjiisistsof  bundles  of  fibrous  connective 
tissue  aggi-egated  into  trabeculse  crossing  one  another 
and   interlacing  in  a   complex   manner.      Numerous 


Fig.  252. — ^Vertical  Section  through  the  Skin  of  Human  Finger. 

fl.  Stratum  comeuin :  h,  stratum  lucidtim  ;  c.  stratum  Malpighii ;  d,  Meissner's, 
or  tactile  corpuscle ;  e,  blood-vessels  cut  across ;  /,  sudoriferous  canal  or 
duct. 

elastic  fibres  are  attached  to  these  trabeculse.  It  con- 
tains groups  of  fat  cells,  in  many  places  arranged  as 
more  or  less  continuous  lobules  of  fat  tissue,  foinning 
the  stratum  adiposam.  These  lobules  are  separated 
by  septa  of  fibrous  connective  tissue  :  their  structure 
and  development,  and  the  distribution  of  the  blood- 
vessels amongst  the  fat  cells,  have  been  described 
(Fig.  41,  and  on  pp.  55  and  56).  The  deep  part  of  the 
subcutaneous  tissue  is  loose  in  texture,  and  contains 
the  large  vascular  trunks  and  big  nerve  branches. 
373.   The    superficial    part    of    the    subcutaneous 


tissue,  or,  as  sonic  liavc  it,  the  deep  part  of  the 
coriiiin,  contains  the  sudoriparous  or  stveat  (jlaiuh. 
Each  gland  is  a  single  tube  coiled  up  into  a  dens"^ 
mass  of  about  -^^  of  an  inch  in  diameter  — in  some 
places,  as  in  the  axilla,  reaching  as  much  as  six  times 
this  size.  From  each  gland  a  duct — the  sudori- 
ferous canal — passes  through  the  corium  in  a  slightly 
wavy  and  vertical  direction  towards  the  epidermis  ; 
it  penetrates  more  or  less  spirally  through  the  inter- 
pajjillary  process  of  the  stratum  Malpighii  and  the 
rest  of  the  ej)idermis,  and  appears  with  an  open  mouth 
on  the  free  surface  of  the  skin. 

The  total  number  of  sweat  glands  in  the  human 
skin  has  been  computed  by  Krause  to  be  over  two 
millions  ;  but  it  varies  greatly  in  different  parts  of  the 
body,  the  largest  number  occurring  in  the  palm  of 
the  hand,  the  next  in  the  sole  of  the  foot,  the  next 
on  the  dorsum  of  the  hand  and  foot,  and  the  smallest 
in  the  skin  of  the  dorsum  of  the  trunk, 

374.  The  sudoriferous  canal  and  the  coiled  tube 
possess  a  distinct  lumen  ;  this  is  lined  with  a  delicate 
cuticle,  especially  marked  in  the  sudoriferous  canal 
and  in  the  commencement  of  the  coiled  tube.  In  the 
epidermis  the  lumen  bordered  by  this  cuticle  is  all 
that  is  present  of  the  sudoriferous  canal.  It  receives 
a  continuation  from  the  deep  layers  of  the  stratum 
Malpighii  and  from  the  basement  membrane  ;  the 
former  is  the  lining  epithelium,  the  latter  the  limiting 
membrana  propria  of  the  sudoriferous  canal.  The 
epithelium  consists  of  two  or  three  layers  of  small 
polyhedral  cells,  each  with  a  spherical  or  oval  nucleus. 

375.  The  structure  of  the  sudoriferous  canal  is, 
then,  a  limiting  membrana  propria,  an  epithelium 
composed  of  two  or  three  layers  of  polyhedral  cells,  an 
internal  delicate  membrane,  and,  finally,  the  central 
cavity,  or  lumen. 

The   first  part — about  one-third  or  one-fourth — 


4o8 


Elements  of  Histology. 


of  the  coiled  tube  (Fig.  253)  is  of  the  same  stnu-ture, 
and  is  directly  continuous  with  the  sudoriferous  canal, 
with  which  it  is  identical,  not  only  in  structure,  but 
in  size.  The  remainder  of  the  coiled  tube — i.e.  the 
distal  part — is  larger  in  diameter,  and  differs  in  these 
essential  respects,  that  its  epithelium  is  a  single  layer 


Fig.  253. — From  a  Section  tlirough  Human  Skin,  showing  the  sweat  gland 
tubes  cut  in  various  directions.     {Atlas.) 

u,  First  part  of  the  coiled  tuljs  seen  in  longitudinal  section ;  b,  the  same  seen 
in  cross-section ;  c,  distal  part  seen  in  longitudinal  section ;   d,  the  same 

seen  in  cross-section. 

of  transparent  columnar  cells,  and  that  tliere  is 
between  this  and  the  limiting  merabrana  propria  a 
kfjjer  of  non-striped  muscle  cells  (Kolliker)  arranged 
parallel  with  the  long  axis  of  the  tube.  In  some 
places,  as  in  the  palm  of  the  hand  and  foot,  in  the 
scrotum,  tlie  nipple  of  the  breast,  the  scalp,  Init 
especially  in  the  axilla,  this  distal  portion  of  the  coiled 
tube  is  of  \evy  great  length  and  breadth,  and  its 
epithelial  cells  contain  a  variable  amount  of  granules. 
It  appears  to  me  that  the  cells  resemble  in  this 
respect  those  of  the   serous    salivary  glands  and  the 


S/c/x.  409 

chief  cells  of  the  gastric  ghmds  (Langley),  inasmuch 
as  they  produce  in  their  interior  hirger  or  siualler 
granules  which  are  used  up  during  secretion,  from  the 
periphery  towards  the  lumen. 

376.  The  ceriiiiiiiioiis  g-laiids  of  the  meatus 
auditorius  externus  are  of  the  same  structure  as  the 
distal  portion  just  described,  except  that  the  inner 
part  of  the  cell  protoplasm  of  the  epithelium  contains 
yellowish  or  brownish  pigment,  found  also  in  their 
secretion — i.e.  in  the  w^ax  of  the  ear. 

Around  the  anus  there  is  an  elliptical  zone,  in  the 
skin  of  which  are  found  large  coiled  gland  tubes — the 
circiim-anal  glands  of  A.  Gay — which  are  identical  in 
structure  with  the  distal  portion  of  the  sweat  gland- 
tubes. 

377.  The  sweat  gland  develops  as  a  solid  cylin- 
drical outgrowth  of  the  stratum  Malpighii  of  the 
epidermis,  which  gradually  elongates  till  it  reaches 
the  superficial  part  of  the  subcutaneous  tissue,  where 
it  commences  to  coil.  The  lumen  of  the  tube  is  of 
later  appearance.  The  membrana  propria  is  derived 
from  the  tissue  of  the  cutis,  but  the  epithelium  and 
muscular  layer  are  both  derived  from  the  original 
outgrowth  of  the  epidermis. 

378.  The  liaii'-follicles  (Fig.  254).— The  skin 
almost  everywhere  contains  cylindrical  yb/Zic^es,  planted 
more  or  less  near  to  one  another,  and  in  groups.  In 
each  of  them  is  fixed  the  root  of  a  hair  ;  that  part  of 
the  hair  which  i^rojects  beyond  the  general  surface  of 
the  skin  is  the  slia/t. 

A  very  few  places  contain  no  hair  follicles,  such, 
for  instance,  as  the  volar  side  of  the  hand  and  foot, 
and  the  skin  of  the  penis. 

Tn  size,  the  hairs  and  hair-follicles  differ  in  dif- 
ferent parts.  Those  of  the  scalp,  the  cilia  of  the  eye- 
lids, the  hairs  of  the  axilla  and  pubic  region,  those  of 
the   male   whiskers   and   moustache,   are    coarse    and 


4TO 


Elemexts  of  Histology. 


thick,  while  the  hairs  of  other  places — e.fj.  the  outer 
surface  of  the  eyelids,  the  inside  of  the  arm  and  fore- 
ann,  etc. — are  very  minute ;  but  as  regards  structure, 
they  are  all  very  much  alike. 

379.   A    complete   hair   and  hair-follicle — that  is, 


trO 


Fig.  254.— Longitudinal  Section  through  a  Human  Hair.     (Atlas.) 

1,  Epidermis;   2,  moutli  of  hair  follicle:  3.  sebaceous  follicle;   4,  musculus 
arrector  pili ;  5,  papilla  of  hair  ;  6,  adipose  tissue. 

the    papillary    hair    of    Unna — shows    the    following 
structure  : — 

The  hair-foUide.  Each  hair-follicle  commences  on 
the  free  surface  of  the  skin  with  a  funnel-shaped 
opening  or  movJlt  :   it   |;asses  in  an  ohlique  direction 


throiiiili  the  corium  into  the  subcutaneous  tissue,  in 
whose  middle  strata — i.e.  in  the  stratum  adiposum — 
it  terminates  with  a  sli^itly  enlarged  extremity,  with 
which  it  is  invaginated  over  a  relatively  small  fungus- 
shaped  papiUa.  This  latter  is  of  tibrous  tissue,  con- 
taining numerous  cells  and  a  loop  of  capillary  blood- 
vessels. 

Minute  hairs  do  not  reach  with  their  follicles  to 
such  a  depth  as  the  large  coarse  hairs,  the  former  not 
extending  wnerallv  much  farther  than  the  deep  part 
of  the  corium.  Degenerating  and  imperfect  hairs  (see 
below)  also  do  not  reach  to  such  a  depth  as  the  perfect 
large  hair  follicles.  In  individuals  with  "  woolly  "* 
hail' — e.g.  the  negro  race  (C.  Stewart),  and  in  animals 
with  *'  woolly  "  hair,  such  as  the  fleece  of  sheep — the 
deep  extremity  of  the  hair-foHicle  is  curved,  sometimes 
even  slightly  upwards. 

380.  The  structure  of  a  liair-folliele  is  as  follows 
(Fig.  255)  :  There  is  an  outer  coat  composed  of  fibrous 
tissue  :  this  is  the  fibrous  coat  of  the  liair-sac.  It  is 
merely  a  condensation  of  the  surrounding  fibrous 
tissue,  and  is  continuous  with  the  papilla  at  the 
extremity  of  the  hair-follicle.  About  the  end  of  the 
hair-follicle,  or  sometimes  as  much  as  in  the  lower 
fourth,  there  is  inside  of  this  tibrous  layer  of  the  hair- 
sac  a  single  contintious  layer  of  transversely  or  circu- 
I a rhj-ar ranged  spimUe-sliaped  ceUs,  each  with  an  oval 
flattened  or  staff"- shaped  nucleus,  completely  resembling, 
and  generally  considered  to  be,  non-striped  muscle- 
cells.  Inside  of  this  layer  of  the  hair-sac  is  a  glassy- 
looking,  hyaline,  basement  membrane,  which  is  not 
very  distinct  in  minute  hairs,  but  is  suthciently  con- 
spicuous in  large  adult  hair-follicles.  This  glassy 
membrane,  as  it  is  called,  is  a  direct  continuation  of 
the  basement  membrane  of  the  surface  of  the  corium, 
and  it  can  be  traced  as  a  delicate  membrane  also  over 
the  surface  of  the  hair-papilla. 


412 


Elements  of  Histology. 


381.  Next 
rootsheath,   the 


to  the  glassy  membrane  is  the  outer 
most  conspicuous  part  of  the  hair- 
follicle.  It  consists  of  a  thick  stratified  epithelium  of 
exactly  the  same  nature  as  the  stratum  Malpighii  of 

the       epidermis, 
I '.     ,. —    ^i^-,^  _  with     which     it 

is    directly    con- 
tinuous,    and 
from     which     it 
developed. 


IS 

In  the  outer 
root  -  sheath  the 
layer  of  cells 
next  to  the  glassy 
membrane  is 
columnar,  just 
like  the  deepest 
layer  of  cells  in 
the  stratum  Mal- 
pighii ;  then  fol- 
low inwards  seve- 
ral layers  of  poly- 
hedral cells;  and, 
finally,  flattened 
nucleated  scales  form  the  innermost  boundary  of  the 
outer  root -sheath.  The  stratum  granulosum  of  the 
stratum  Malpighii  is  not  continued  beyond  the  mouth 
of  the  hair-follicle,  but  there  it  is  generally  very  marked. 
The  outer  root-sheath  becomes  greatly  attenuated  at 
the  papilla — in  fact,  it  is  there  continuous  with  the 
cells  constituting  the  hair-bulb. 

382.  The  centre  of  the  hair-follicle  is  occupied  by 
the  root  of  the  hair,  which  terminates  with  an  enlarged 
extremity — the  Itair-hulb ;  this  grasps  the  whole 
papilla.  The  hair-bulb  is  composed  of  polyhedral 
ei)ithelial  cells,  separated  from  one  another  by  cement 
substance,   and  continuous  with  the  cells  of  the  ex- 


Fig.  255. — Cross-section  through  a  Hiunau  Hair 
and  Hair- follicle. 

«,  ^farrow  of  liair;  h.  cortex  of  hair;  c,  cuticle  of 
hair ;  d,  Huxley's  layer  of  inner  root-sheath  ;  e, 
Henle's  layer  of  inner  root-sheath ;  /.  outer  root- 
sheath ;  g,  glassy Jiienibrane;  /(, fibrous  coat  of  hair- 
sac  ;  i,  lymph  spaces  in  the  same. 


Sa'/n.  4 1 3 

tremity  of  tlie  outer  root-sheatli,  from  wliicli  they 
originate  in  the  first  instance  ;  just  over  the  papilla 
there  is  a  special  row  of  sJiort  cohunnar  cells,  which 
are  in  an  active  state  of  multiplication,  in  consequence 
of  which  new  cells  are  constantly  being  formed  over 
the  papilla.  As  a  result  of  this  there  is  a  gradual 
pushing  outwards,  within  the  cavity  of  the  hair- 
follicle,  of  the  cells  previously  formed  ;  these  cells 
form  the  hair  itself.  Nearest  to  the  papilla  all  the 
cells  of  the  hair  are  polyhedral,  farther  outwards — i.e. 
towards  the  surface  of  the  skin — they  become  more 
elongated  and  spindle-shaped,  and  constitute  the  cells 
of  the  hair-substance  ;  except  in  the  very  centre  of  the 
hair,  where  they  remain  polyhedral,  so  as  to  represent 
the  cells  of  the  marrow  of  the  hair,  and  in  the  peri- 
phery of  the  hair,  where  they  remain  more  or  less 
polyhedral,  so  as  to  form  the  inner  root-sheath. 

383.  The  root  of  the  liair,  except  at  the  hair- 
bulb,  shows  the  following  parts  :  The  substance  of  the 
hair,  the  cuticle,  and  the  inner  root-sheath.  The 
substance  of  the  hair  is  composed  of  the  hair -fibres — 
i.e.  long  thin  fibres,  or  narrow  long  scales,  each  com- 
posed of  hyaline  horny  substance,  and  possessed  of  a 
thin  staff-shaped  remnant  of  a  nucleus.  These  are 
held  together  by  a  certain  amount  of  interstitial 
cement  substance.  Towards  the  bulb  they  gradually 
change  into  the  spindle-shaped  cells  above  mentioned. 
They  can  be  isolated  by  strong  acids  and  alkalies.  In 
pigmented  hairs  there  occur  numerous  figment 
(jranules  between  the  hair-fibres,  but  also  diffused 
pigment  in  their  substance.  The  same  is  noticed  with 
reference  to  the  hair-bulb — namely,  pigment  granules 
being  present  in  the  intercellular  cement,  and  pig- 
ment also  in  the  cell  substance.  In  the  centre  of 
many  hairs  is  a  cylindrical  marroiv,  containing 
generally  one  row  of  ])olyhedral  cells,  which  are,  to  a 
great  extent,  filled  with  air. 


414 


Elements  of  Histology. 


a    I 


•384.  On  the  surface  of  the  haii--substance  is  a  thin 
cuticle,  a  single  layer  of  horny  non-nucleated  hyaline 
scales  arranged  more  or  less  transversely ;  they  are 
imljiicated,  and,  according  to  the  degree  of  imbrica- 
tion, the  cuticle  shows  more  or  less  marked  projec- 
tions, which  give  to  the  circumference 
of  the  hair  the  appearance  of  minute 
teeth,  like  those  of  a  saw. 

385.  The  inner  root-sheath  in 
well-formed,  thick  hairs  is  very  dis- 
tinct, and  consists  of  a  delicate  cuticle 
next  to  the  cuticle  of  the  hair  ;  then 
an  inner,  or  Huxley's,  layer,  which 
is  a  single,  or  sometimes  double,  layer 
of  horny  cubical  cells,  each  with  a 
remnant  of  a  nucleus ;  and,  finally, 
an  outer,  or  HenleJs,  layer — a  single 
layer  of  non-nucleated  horny  cubical 
cells. 

The  shaft  of  the  hair  (Fig.  256), 
or  the  part  projecting  over  the  free 
surface  of  the  skin,  is  of  exactly  the 
same  structure  as  the  root,  except  that 
it  possesses  no  inner  root-sheath. 
386.  As  mentioned  above,  at  the  hair-bulb  the 
polyhedral  cells  constituting  this  latter  gradually  pass 
into  the  different  parts  of  the  hair — i.e.  marrow-sub- 
stance, cuticle,  and  inner  root-sheath — and  the  con- 
tinual new  production  of  cells  over  the  jmpilla  causes  a 
gradual  progression  and  conversion  of  the  cells,  and  a 
corresponding  growth  in  length  of  the  hair. 

Pigmented  hairs,  as  mentioned  above,  contain  pig- 
ment granules  between — i.e.  in  the  interstitial  sub- 
stance cementing  together — the  hair-fibres,  and  diffuse 
pigment  in  their  substance.  According  to  the  amount 
of  these  pigments,  but  especially  of  the  interstitial 
pigment  granules  (Pincus),  the  colour   of  the  hair  is 


Fig.  -2.56. —Longitu- 
dinal View  of  the 
Shaft  of  a  Pig- 
mented Human 
Hair. 


ilarroAV  of 
b,  fibres  of 
substance  ; 
cuticle. 


hair  ; 

liaii- 

c. 


Sa'/x. 


415 


of  a  greater  or  lesser  dark 
is  oliieHy  ditlVise  pigment, 
neither  the  one  nor  the 
other  pigment  is  present : 
in  grey  there  is  air  at  least 
in  the  superficial  layers  of 
the  hair  substance,  besides 
absence  of  pigment. 

Sleek  hairs  are  circular, 
curly  oval,  in  cross-section. 
Sleek  hairs  are  implanted 
with  their  h  a  i  r  -  b  u  1  b 
straight  ;  in  curly  hairs  the 
hair-bulb  forms  a  more  or 
less  pronounced  hook.  This 
is  the  cause  for  the  more 
or  less  si)iral  twisting  of 
the  hair-shaft  of  curly  hairs 
during  its  growth  outwards. 

387.  Xew  formation 
of  liair  (Fig.  257). — 
Every  hair,  be  it  fine  and 
short  or  thick  and  long, 
\mder  normal  conditions, 
has  only  a  limited  exist- 
ence, for  its  hair-follicle, 
including  the  papilla,  sooner 
or  later  undergoes  degener- 
ation, and  subsequent  to 
this  a  new  papilla  and  a 
new  hair  are  formed  in  its 
place.  What  happens  is 
this — the  lower  part  of  the 
hair-follicle,  including  the 
papilla  and  hair-bulb,  de- 
generate and  are  gradu- 
ally absoi'bed.     Then  there 


tint,     in  red  luiirs  there 
In  white  or  albino  hairs 


fe''i'l't.:->.?      -^ 


Fig.  257. — From  a  section  through 
Human  Scalp,  showing  a  degen- 
erating hair.     (Atlas.) 

a.  Epidermis ;  b,  hair ;  c,  outer  root- 
sheath  of  hair  follicle  ;  d,  sebace- 
ous follicle;  f,  arrector  pili ;  /, 
cyst  grown  out  of  the  outer  root- 
sheath;  g,  hair-kuob  ;  h,  new  out- 
growth of  the  outer  root-sheath  ; 
/,  new  papilla. 


4i6  Elements  of  Histology. 

is  left  only  the  uj^per  part  uf  the  follicle,  and  in  the 
centre  of  this  is  the  remainder — i.e.  non-degenerated 
portion — of  the  hair-root.  The  fibres  of  this  are  at 
the  extremity  fringed  out  and  lost  amongst  the  cells 
of  the  outer  root-sheath  of  the  follicle.  This  repre- 
sents the  hair-knoh  (Henle).  Xow,  from  the  outer 
root-sheath  a  solid  cylindiical  outgrowtli  of  epithelial 
cells  into  the  depth  takes  place  ;  against  the  extremity 
of  this  a  new  papilla  is  formed.  In  connection  with 
this  new  papilla,  and  in  the  centre  of  that  cylindrical 
outgrowth,  a  new  hair-bulb  and  hair  are  formed,  and 
as  the  latter  gradually  mows  outwards  towards  the 
surface,  it  lifts,  or  rather  pushes,  the  old  hair — i.e. 
the  hair-knob — out  of  the  follicle.  The  outer  part  of 
the  follicle  of  the  old  hair  persists. 

Thus  we  find  in  all  parts  of  the  skin  where  hairs 
occur  complete  or  j^apillarv  hairs  side  by  side  with 
degeneratincT  hairs  or  hair-knobs. 

388.  Developiiieiit  of  liair. — In  the  human 
fcetus  the  liair-follicles  make  their  first  appearance 
about  the  end  of  the  third  m.onth,  as  solid  cylindrical 
outgrowths  from  the  stratum  INIalpighii.  This  is  the 
rudiment  of  the  outer  root-sheath.  After  having  pene- 
trated a  short  distance  into  the  corium,  this  latter 
becomes  condensed  around  it  as  the  rudiment  of  the 
hair-sac.  and  at  the  distal  extremity  forms  the  papilla 
2:rowinc(  against  the  outer  root  sheath  and  invajicin- 
ating  it.  On  the  surface  of  the  papilla  a  rapid  mul- 
tiplication of  the  epithelial  cells  of  this  extremity  of 
the  outer  root-sheath  takes  place,  and  this  forms  the 
hair-bulb,  by  the  multiplication  of  whose  cells  the  hair 
and  the  inner  root-sheath  are  formed.  As  growth 
and  multij^lication  proceed  at  the  hair  bulb,  so  the 
new  hair,  with  its  pointed  end,  gradually  reaches  the 
outer  surface.  It  does  not  at  once  penetrate  the 
epidermis,  but  remains  growing  and  burrowing  its 
wav  for  some   time   in   the   stratum   corneum  of  the 


Sa'/.v. 


417 


epidermis  in  a  more  or  less  horizontal  direction,  till  it 
finally  lifts  itself  out  of  this  beyond  the  free  surface. 

3iS9.  In  many  mammals  occur,  amongst  ordinary 
hairs,  special  large  hairs,  with  huge  hair-follicles 
planted  deeply  into  the    subcutaneous  tissue ;    such 


Fig.   25S.— Section   througli  the   «kiii  nf  tlie   Lip  of  a  Rabbits   Mouth. 
(Fhotorjraph.     Loiv  power.) 

Small  ordinary  hair-follicles,  one  hirge  tactile  hair  and  hair-follicle.  Tlie  dark 
thick  hoiindarj-  is  the  tissue  of  the  hair-sac.  the  clear  parts  in.side  are  the 
masses  of  blood  spaces,  the  dark  line  next  to  the  hair  itself  is  the  outer 
root-sheath. 


are  the  big  hairs  in  the  skin  about  the  lips  of  the  mouth 
in  the  dog,  cat,  rabbit,  guinea-pig,  mouse  and  rat,  etc. 
These  are  the  tactile  hairs  (Fig.  258).  Their  hair-follicle 
possesses  a  thick  hair-sac,  in  which  are  contained  large 
sinuses  intercommunicating  with  one  another  and 
with  the  blood  system ;  these  sinuses  are  separated 
B   B 


41 8  Elemexts  of  Histology. 

\)\  trabecul?e  of  non-strined  muscular  tissue,  and 
represent,  therefore,  a  cavernous  tissue.  The  papilla 
is  large,  and  so  is  the  outer  root-sheath  and  the 
hair-root  in  all  its  parts.  There  are  vast  numbers  of 
nerve-fibres,  distributed  and  terminating  amongst  the 
cells  of  the  outer  root-sneath  (Arnstein). 

390.  With  each  hair- follicle  are  connected  one  or 
tvro  sehaceous  foUirles.  These  consist  of  several  fiask- 
shaped  or  oblong  alveoli,  joined  into  a  common  short 
duct  opening  into  the  hair-follicle  near  the  surface — 
i.e.  that  part  called  the  neck  of  the  hair-follicle. 

The  alveoli  have  a  limiting  membrana  propria ; 
next  to  this  is  a  layer  of  small  polyhedral,  granular- 
looking  epithelial  cells,  each  with  a  spherical  or  oval 
nucleus  ;  next  to  this,  and  filling  the  entire  cavity  of 
the  alveolus,  are  large  polyhedral  cells,  each  with  a 
■-spherical  nucleus  :  the  cell  substance  is  filled  with 
minute  oil  globules,  between  which  is  left  a  sort  of 
honeycombed  reticulated  stroma.  The  cells  nearer  to 
the  centre  of  the  alveolus  are  the  largest.  Towards 
the  duct  they  become  shrivelled  \\\}  into  an  amorphous 
mass.  The  duct  itself  is  a  continuation  of  the  outer 
root-sheath. 

As  multiplication  goes  on  in  the  marginal  layer  of 
epithelial  cells — i.e.  those  next  the  membrana  proprise 
— the  products  of  this  multiplication  are  gradually 
shifted  forward  towards  the  duct,  and  through  this 
into  the  neck  and  rnoutli  of  the  hair-follicle,  where 
they  constitute  the  elements  oi  sehuin. 

There  is  a  very  characteristic  misproportion  be- 
tween the  size  of  the  hair-follicle  and  that  of  the 
sebaceous  gland  in  the  embryo  and  newly-ljorn,  the 
.sebaceous  cjland  Ijeing  there  so  larije  that  it  forms  the 
most  conspicuous  part,  the  minute  hairs  (lanugo) 
being  situated,  as  it  were,  in  the  duct  of  the  sebaceous 
follicle. 

391.  In  connection   with   each  hair-follicle,  espe- 


Sa'/jv. 


419 


daily  where  they  are  of  good  size — as  in  the  scalp — 
there  is  a  bundle,  or  rather  group  of  bundles,  of  non- 
sti-iped  muscular  tissue  ;  this  is  tlie  arrector  pili.  It  is 
inserted  in  the  liaii--sac  near  the  bulbous  portion  of  the 


Fig.  259. — Vertical  Section  through  the  Human  Xail  and  Nail-bed. 

a.  Stratum  Malpigbii  of  uail-bed;  I),  stratum  .arrauulosuin  of  uail-bed  •  c    Aeev 
layers  of  nail  sulistaucc  ;  d,  superfieiallayers  of  same.        '    ' 

hair- follicle,  and  passes  in  an  oblique  direction  towards 
the  surface  of  the  coriuni,  grasping,  as  it  were,  on  its 
way  the  sebaceous  follicle,  and  terminating  near  the 
papillary  layer  of  the  surface  of  the  corium.  The 
arrector  pili  forms  with  the  hair-follicle  an  acute 
angle — this  latter  being  planted  into  the  skin  in  an 


42 o  Elements  of  Histology. 

oblique  direction,  as  mentioned  above — and  conse- 
quently, when  the  arrector  contracts,  it  has  the  effect 
of  raising  the  hair-follicle  and  hair  (cutis  anserina — 
"goose's  skin  '),  and  of  making  the  hair  assume  a 
more  upright  position  (causes  it,  as  we  say,  to  "  stand 
on  end ").  At  the  same  time,  it  compresses  the 
sebaceous  follicle,  and  thus  facilitates  the  discharge  of 
the  sebum. 

392.  The  corium  of  the  scrotum,  of  the  nipple  of 
the  breast,  of  the  labia  pudendi  majora,  and  of  the 
penis,  contains  numbers  of  bundles  of  non-striped 
muscular  tissue  (Kolliker),  independent  of  the  hairs  ; 
these  run  in  an  oblique  and  horizontal  direction,  and 
form  plexuses. 

393.  The  nails  (Fig.  259).— We  distinguish  the 
hody  of  the  nail  from  the  free  margin  and  from  the 
root ;  the  body  is  the  nail  proper,  and  is  fixed  on  to 
the  nail-bed,  while  the  nail-root  is  fixed  on  the  nail- 
matrix — i.e.  the  posterior  j)art  of  the  nail-bed.  The 
nail  is  inserted,  with  the  greater  part  of  its  lateral  and 
wdth  its  posterior  margin,  in  the  nail-groove,  a  fold 
by  which  the  nail-matrix  passes  into  the  surrounding 
skin. 

394.  The  substance  of  the  nail  is  made  up  of  a 
large  number  of  strata  of  homogeneous  horny  scales  — 
the  nail-cells — -each  with  a  staff-shaped  remnant  of  a 
nucleus. 

The  corium  of  the  nail-bed  is  higlily  vascular  :  it 
is  firmly  fixed  by  stifi"  bands  of  fibrous  tissue  on  the 
subjacent  periosteum  ;  it  is  covered  with  a  stratum 
]\Ialpighii  of  the  usual  description,  except  that  the 
stratum  irranulosum  is  absent  in  the  nail-matrix,  but 
is  present  in  a  rudimentary  state  in  the  rest  of  the 
nail-bed.  The  nail  itself  rej^resents  the  stratum 
lucidum,  of  course  of  exaggerated  thickness,  situated 
over  the  stratum  Malpighii  of  the  nail-bed.  There 
is  no  stratum  corneum  over  the  nail. 


The  stratum  Malpighii  and  coriuni  of  the  nail-bed 
are  placed  into  permanent  minute  folds,  and  the  nail 
possesses  on  its  lower  surface  corresponding  linear 
indentations. 

395.  In  the  foetal  nail-bed  the  stratum  Malpighii 
is  covered  with  the  usual  stratum  lucidum  and  stratum 
corneum,  but  the  former  is  the  larger  :  by  a  rapid 
multiplication  of  the  cells  of  the  stratum  Malpighii, 
and  a  conversion  of  its  superficial  cells  into  the  scales 
of  the  stratum  lucidum.  the  fcetal  nail  is  produced. 
At  this  early  stage  the  nail  is  covered  by  stratum 
corneum.  By  the  end  of  the  fifth  month  the  nail 
marcrin  breaks  throuijh  this  stratum  corneum.  and  bv 
the  seventh  month  the  greater  part  of  tlie  nail  has 
become  clear  of  it. 

306.  Till'  bIood-ves«»eIs  of  the  »kiii. — The 
blood-vessels  are  arranged  in  diflerent  system <  for  the 
different  parts  of  the  skin  (Tomsa)  : — 

{(()  There  is.  fir^^t,  the  vascular  sy.stem  of  the 
adipose  tissue,  diflering  in  no  way  from  the  dis- 
tribution of  blood-vessels  in  fat  tissue  of  other  places. 

(6)  Then  there  is  the  vascular  system  of  the  hair- 
follicle.  The  papilla  has  a  capillary  loop,  or  rather 
a  minute  arteriole,  a  capillary  loop,  and  a  descending 
vein,  and  the  fibrous  ti.ssue  of  the  hair-sac  possesses 
capillaries  arranged  as  a  network  with  elongated 
meshes,  with  its  afferent  arteriole  and  eflerent  vein. 

(c)  The  sebaceous  follicle  has  its  afferent  arteriole 
and  eflerent  vein,  and  capillary  networks  surrounding 
the  alveoli  of  the  gland.  The  arrector  pili  and  other 
bundles  of  non-striped  muscular  tissue  possess  capil- 
lary networks  \\  ith  elongated  meshes. 

(d)  The  sweat  glands  have  an  afferent  arteriole, 
from  which  proceeds  a  veiy  rich  network  of  capil- 
laries, twining  and  twisting  round  the  gland-tube. 
The  duct  possesses  its  separate  aff'erent  arteriole  and 
capillaries,  forming  elongated  meshes. 


42  2  Elements  of  Histology. 

(e)  The  last  arterial  branches  are  those  that  reach 
the  surface  of  the  corium,  and  there  break  up  into  a 
dense  capillarv  network  with  loops  for  the  papillae. 
In  connection  with  these  capillaries  is  a  rich  plexus  of 

veins  in  the  superficial  layer  of  the  corium. 


Fig.  -260.  —Skin  of  the  Web  of  Frog  of  which  the  lymphatics  had  been  in- 
°  jected,  showing  the  dense  plexus  of  lympliatic  vessels.     {Photograph. 
Lov:  poi'-er.) 

(/)  In  the  nail-bed  are  dense  networks  of  capil- 
laries, with  loops  for  the  above-named  folds. 

397,  The  lysiipliatics  (Fig.  260). — There  are  net- 
works of  lymphatic  vessels  in  all  strata  of  the  skin  ; 
they  are,  more  or  less,  of  horizontal  expansion,  with 
oblique  branches  passing  l^etween  them.  Their  wall 
is  a  sinfde  laver  of  endothelial  cells,  and  some  of  them 
possess  valves.      Those  of  the  surface  of  the  corium 


Sa'/x.  4-3 

take  up  lyiuplKitics  of  the  papilla?.  The  subcutaneous 
lymphatics  are  the  biggest.  The  fat  tissue,  the  sweat- 
glands,  and  the  hair-follicles  possess  their  own  lym- 
phatic clefts  and  sinuses.  The  interfascicular  spaces 
of  the  corium  and  subcutaneous  tissue  are  directly 
continuous  with  the  lymphatic  vessels  in  these  parts. 

398.  The  iierve^». — The  nerve-branches  break  up 
into  a  dense  plexus  of  fine  nerve  fibres  in  the  super- 
ficial layer  of  the  corium.  This  plexus  extends  hori- 
zontally, and  gives  ofi"  numerous  elementary  fibrils 
to  the  stratum  Malpighii,  in  which  they  ascend  verti- 
cally and  in  a  more  or  less  wavy  fashion  towards  the 
stratum  lucidum  (Langerhans,  Podkopaefi",  Eberth, 
Eimer,  Ranvier,  and  others).  According  to  some, 
they  teraiinate  with  a  minute  swelling  ;  according  to 
others,  they  form  networks ;  according  to  more 
recent  observations,  some  of  the  fibrils  terminate 
also  in  the  substance  of  the  deep  epithelial  cells  {see 
Chap.  XIV.). 

The  subcutaneous  nerve-branches  of  some  places 
— palm  of  hand  and  foot,  and  skin  of  penis — give 
off'  single  niedullated  nerve  fibres,  terminating  in  a 
Pacinian  corpuscle,  mentioned  in  a  former  chapter. 
In  the  volar  side  of  the  fingers  and  toes  there  occur 
in  some  of  the  papillfe  of  the  corium  the  tactile  or 
Meissner's  corpuscles,  each  connected  with  one  or  two 
meduUated  nerve  fibres,  as  described  in  a  previous 
chapter.  The  outer  root-sheath  of  the  hair-follicles 
contains  the  terminations  of  fine  nerve  fibres,  in  the 
shape  of  primitive  fibrillte  (Jobert,  Bonnet,  and 
Arnstein).  According  to  Jobert,  the  nerve  fibres 
entwine  the  hair-follicle  in  circular  turns.  The 
tactile  hairs  possess  a  greater  supply  of  nerves  than 
the  ordinary  hair-follicles. 


424 


CHAPTEE    XXXVII. 

THE    CONJCXCTIVA    AXD    ITS    GLANDS. 

399.  (1)  The  eyelids  (Fig.  261).— The  outer 
layer  of  the  eyelids  is  skin  of  ordinary  description  : 
the  inner  is  a  delicate,  highly  vascular  membrane — 
the  conjunctiva  palpehrcn.  This  includes  a  firm  plate 
— the  tarsal  plate. — which  is  not  cartila^re,  but  very 
dense,  white,  fibrous  tissue.  In  it  lie  embedded  the 
Meibomian  glands.  These  extend  in  each  eyelid  in  a 
vertical  direction  from  the  distal  margin  of  the  tarsal 
plate  to  the  free  margin  of  the  eyelid  :  in  the  posterior 
angle  of  this  margin  lies  the  opening  or  mouth  of  each 
of  the  Meibomian  glands. 

The  duct  of  a  Meibomian  gland  is  lined  with  a 
continuation  of  the  stratified  pavement  epithelium, 
lining  the  free  margin  of  the  lid  :  it  passes  in  the 
tarsal  plate  toward  its  distal  margin,  and  takes  up  on 
all  sidi-s  sliort  minute  ducts,  each  of  which  becomes 
enlarged  into  a  spherical,  saccular,  or  llask-shaped 
alveolus.  This  is  identical  in  structure  and  secretion 
icith  the  alveoli  of  the  sebaceous  follicles  of  the  skin. 

400.  The  conjunctival  layer  is  separated  from  the 
subcutaneous  tissue  of  the  skin  layer  of  the  eyelid  by 
the  bundles  of  the  sphincter  nrbicidaris — striped  mus- 
cular tissue.  Some  bundles  of  this  extend  near  the 
free  margin  of  the  lid,  and  represent  what  is  known 
as  the  musculus  ciliaris  Riolani.  This  sends  bundles 
around  the  mouth  of  the  ^Meibomian  ducts. 

401.  At  the  anterior  angle  of  the  free  margin  of 
the  lid  are  the  evelashes  or  cilia,  remarkable  for  their 


Conjunctiva  and  its  Glands. 


425 


thickness  and  rapid  reproduction.      Xear  the  cilia,  Viut 
towards    the    ^leiboniian    ducts,    open    the    ducts    of 


.9 


\iT&, 


-  ^®  "P^^- 


yh 


*:■$• 


Y-^ 


K. 


"=S^ 


Fig.  -261.— Vertical  Section  through  the  Upper  Eyelid.     (Waldeger.) 

1    CoDfunetiva  •  2,  skin  ;  3.  permanent  folds  of  the  conjunctiva ,-  4,  bundles  of 

'    the  sphincter  orbicularis;  5,  eyelashes  :  6.  mouth  of  the  gland  of  ilohl  ;  7, 

duct  of  the  Meibomian  gland  :  >,  tarsal  gland>. 

peculiar  large  glands — the  glands  of  Mold.     Each  of 
these  is  a  wavy  or  spiral  tul>e,  pa^^sing  in  a  vertical 


426  Elements  of  Histology. 

direction  from  the  margin  of  the  lid  towards  its  distal 
part ;  it  comjdetely  coincides  in  structure  with  the 
large  portion  of  a  sweat  gland — i.e.  that  part  contain- 
ing a  columnar  epithelial  lining,  and  between  this  and 
the  membrana  propria  a  longitudinal  layer  of  non- 
striped  muscular  cells. 

The  free  margin  is  covered,  as  mentioned  above, 
with  stratified  pavement  epithelium,  into  which  the 
mucous  membrane  extends  in  the  shape  of  minute 
papillae.  In  the  conjunctiva  palpebral  the  epithelium 
is  a  thin  stratified  pavement  epithelium  ;  there  are 
no  papilhe,  but  the  sub-epithelial  mucosa — that  is,  the 
layer  situated  between  the  epithelium  of  the  surface 
and  the  tarsal  plate — contains  a  dense  network  of 
capillary  blood-vessels. 

402.  Passing  from  the  eyelids  on  to  the  eyeball, 
we  have  the  continuation  of  the  conjunctiva  palpebrse 
— i.e.  the  fornix  conjunctivae — -and,  further,  the  con- 
junctiva fixed  to  the  sclerotic,  and  terminating  at  the 
margin  of  the  cornea — the  conjunctiva  l)ul])i.  The 
epithelium  covering  the  conjunctiva  fornicis  and  con- 
junctiva bulbi  is  stratified  epithelium,  the  superficial 
cells  being  short  columnar  ;  next  to  the  fornix  the 
superficial  cells  are  beautiful  columnar,  and  the 
mucosa  underneath  the  epithelium  is  placed  in  regular 
folds  (Stiedn,  Waldeyer).  Towards  the  cornea  the 
epithelium  of  the  conjunctiva  assumes  the  character 
of  stratified  pavement  epithelium,  and  minute  papillae 
extend  into  it  fi-om  the  mucosa. 

403.  The  mucous  membrane  is  fibrous  tissue,  con- 
taining the  networks  of  capillary  blood-vessels. 

Into  the  fornix  lead  minute  mucous  glands,  em- 
bedded in  the  conjunctiva  fornicis;  they  are  the  glands 
of  Krause.  Similar  glands  exist  in  the  distal  "portion 
of  the  tarsal  plate. 

404.  The  blood-vessels  of  the  conjunctiva 
terminate  as  the  capillary  network  of  the  su])erficial 


Conjunctiva  and  its  Glands.  427 

layer  of  the  mucosa,  and  as  capillaiy  networks  for  the 
Meibomian  glands,  Krause's  gland,  etc.  Around  the 
corneal  margin  the  conjunctival  vessels  are  particu- 
larly dense,  and  loops  of  ca})illaries  extend  from  it 
into  the  very  margin  of  the  cornea. 

405.  The  lyiii|>liafic«»  form  a  superficial  and 
deep  network.  Both  are  connected  by  short  branches. 
The  deep  vessels  are  possessed  of  valves.  The  super- 
ficial plexus  is  densest  at  the  limbus  cornese,  and  they 
are  in  direct  connection  with  the  interfascicular  lymph 
clefts,  both  of  the  sclerotic  and  cornea.  In  the 
margin  of  the  lid  the  superficial  lymphatics  of  the  skin 
anastomose  with  those  of  the  conjunctiva. 

Lymph  follicles  occur  in  groups  in  the  conjunctiva 
of  many  mammals  about  the  inner  angle  of  the  eye. 
In  the  lower  eyelid  of  cattle  they  are  very  conspicuous, 
and  known  as  the  glands  of  Bruch.  They  are  also 
well  marked  in  the  third  lid  of  many  mammals. 

According  to  Stieda  and  Morano,  isolated  lymph 
follicles  occur  also  in  the  human  conjunctiva. 

406.  The  nerves  are  very  numerous  in  the  con- 
junctiva ;  they  form  plexuses  of  non-medullated  fibres 
underneath  the  epithelium.  From  these  plexuses  fine 
fibrils  pass  into  the  epithelium  of  the  surface,  between 
whose  cells  they  terminate  as  a  network  (Helfreich, 
Morano).  End  bulbs  of  Krause  occur  in  great 
numbers  in  man  and  calf.  They  have  been  mentioned 
in  a  former  chapter. 

407.  (2)  The  lacliryiiial  g-laiids  are  identical 
in  structure  with  the  serous  or  true  salivary  glands. 
The  arrangement  of  the  connective-tissue  stroma,  the 
nature  and  structure  of  the  ducts — especially  of  the 
intralobular  ducts— and  alveoli,  the  distribution  of 
blood-vessels  and  lymphatics,  are  exactly  the  same 
as  in  the  true  salivary  glands.  Reichel  has  found 
that  the  epithelial  cells  lining  the  alveoli  are  well 
defined,  conical  or  cylindrical,  transparent,  and  slightly 


428  Elements  of  Histology. 

granular  during  rest  ;  but  during  secretion  they  grow 
smaller,  more  opaque  and  more  granular,  their  outlines 
are  not  well  defined,  and  the  nucleus  becomes  more 
spherical  and  placed  more  centrally. 

408.  In  most  mammals  there  is  in  the  inner  angle 
of  the  eye,  and  closely  placed  against  the  surface  of 
the  eyeball,  a  gland  called  Harder's  (jiand.  Accord- 
ing to  Wendt,  this  is  either  a  true  serous  gland,  like 
the  lachrymal — as  in  the  ox,  sheep,  and  pig — or  it  is 
identical  in  structure  with  a  sebaceous  gland,  as  in 
the  mouse,  rat,  and  guinea-pig  ;  or  it  consists  of  two 
portions,  one  of  which  (white)  is  identical  with  a 
sebaceous,  while  the  other  (rose-coloured)  is  a  true 
serous  gland  ;  such  is  the  case  in  the  rabbit  and  hare 
According  to  Giacomini,  a  rudiment  of  Harders  gland 
exists  also  in  the  ape  and  man. 


429 


CHAPTER  XXXVIII. 

CORNEA,     SCLEROTIC,      LIGAMENTUM      PECTINATUM      AND 
CILIARY    MUSCLE. 

400.  T.  The  roriiea  (Fig.  262)  of  man  and  many 
mauiDials  consists  of  the  following  layers,  counting 
from  front  to  back  : — 

(1)  The  epithelium  of  the  anterior  surface  [see 
Fig.  26).  This  is  a  very  transparent,  stratified  pave- 
ment epithelium,  such  as  has  been  described  in  par. 
22.  It  is  directly  continuous  with  the  epithelium  of 
tlie  conjunctiva,  but  it  is  more  transparent;  in  dark 
pigmented  eyes  of  mammals  the  epithelium  of  the 
conjunctiva  is  also  pigmented.  In  these  cases  the 
pigment,  as  a  rule,  does  not  pass  beyond  the  margin 
of  the  cornea. 

410.  (2)  Next  follows  a  homogeneous  elastic  mem- 
brane, Bowman^s  'ineinhrane,  or  elastica  anterior.  It 
is  best  shown  in  the  human  eye,  but  is  present,  even 
though  only  rudimentary,  in  the  eye  of  mammals. 

(3)  Then  follows  the  ground  suhstaiice,  or  sub- 
stantia propria,  of  the  cornea.  This  is  composed  of 
iamelhe  of  bundles  of  fibrous  connective  tissue. 
Neiofhbourinor  lamellse  are  connected  with  one  another 
by  oblique  bundles. 

The  fibre  bundles  within  each  lamella  run  parallel 
to  the  surface  of  the  cornea,  but  may  cross  one 
another  under  various  angles. 

In  the  anterior  layer  of  the  ground  substance  some 
of  the  bundles  pass  through  several  lamellae  in  an 
oblique  manner ;  they  represent  the  librse  arcuatse. 


43° 


Elements  of  Histology. 


The  fibrils  within   the  bundles,  and   the  bundles, 
and  the  lainelhv  of  bundles  are  held  together  by  an 

interstitial,  albu- 
;g7  niinous,  semi-fluid  ce- 
ment sul)stance,  which, 
like  other  similar  in- 
tei'stitial  substances, 
belono's  to  the  globu- 
lins,  and  is  soluble  in 
10  per  cent,  saline 
solution  (Schweigger 
Seidel).  A  few  elastic 
tibrils  are  seen  here 
and  thei'e.  Between 
the  lamellae  are  left  the 
lacunas  and  canal iculi 
for  the  branched,  flat- 
tened, nucleated,  cor- 
neal corpuscles^  de- 
scribed in  a  previous 
chapter  (Figs.  37,  38). 
They  anastomose  with 
one  another  within  the 
same  plane,  and  also, 
to  a  limited  degree, 
with  those  of  neigh- 
bouring planes. 

411.  (4)Thenieni- 
l>i'aiia  Desceiiioti, 
or  elastica  posterior, 
is  a  resistant  elastic 
membrane,  conspic- 
uous by  its  thickness 
in  all  corne?e, 

(5)  The  posterior 
surface  of  this  mem- 
l^rane  is   covered  with 


Fig.  2(32. — From  a  Vertieal  Section 
through  the  Membranes  of  the  Eve  of  a 
Child.     {Atlas.) 

a.  Cornea;  b,  sclerotic  :  c.  \v\>  ;  d,  processus 
ciliaris;  e,  ligameunnn  pectinatiiui  :  /, 
ciliary  imisck",  Its  meridional  bundles;  n 
choroid  membrane;  h.  retina  of  the  nra 
serrata;  i,  sphincter  piipilla^  in  cross- 
section. 


Cornea.  431 

a  mosaic  of  ])eautit'vil  pohjijomd  endotlielidJ  ceUs^ 
eacli  with  an  oval  nucleus — the  endotheliuiii  of 
Descemet's  membrane.  Under  stimulation  these 
cells  contract.  At  first  they  appear  slightly  and 
numerously  branched,  but  gradually  their  processes 
become  longer  and  fewer,  and  ultimately  they  are 
reduced  to  minute  clumps  of  nucleated  protoplasm, 
each  with  a  few  long  processes. 

There  are  no  blood-vessels  in  the  normal  cornea, 
except  in  fretal  life,  when  there  is  underneath  the 
anterior  epithelium  a  plexus  of  capillaries. 

The  lymphatics  are  represented  as  the  intercom- 
municating lymjih-canalicular  system — i.e.  the  lacun?e 
and  canaliculi  of  the  corneal  corpuscles  ;  and  in  con- 
nection with  these  are  lymph  channels  lined  with  a 
continuous  endothelium  and  containing;  the  nerve 
bundles. 

412.  The  nerves  (Figs.  103,  105,  106)  are  distri- 
buted as  the  nerves  of  the  anterior  layers,  and  as 
those  of  the  Descemet's  membrane.  The  first  form 
rich  plexuses  of  tibrillated  axis  cylinders,  with  trian- 
gular nodal  points  (Cohnheim),  in  the  anterior  layers 
of  the  ground  substance ;  from  this  plexus  pass 
obliquely  through  Bowman's  membrane  short  branches 
— the  rami  perforantes  (Kfilliker) — and  these  imme- 
diately underneath  the  epithelium  break  up  into  their 
constituent  primitive  fibrils,  the  latter  coming  off 
the  former  brush-like  (Cohnheim).  These  primitive 
fibrilhe  ultimately  ascend  into  the  anterior  epithelium 
(Hoyer,  Cohnheim,  and  others),  where  they  branch, 
and  nearly  reach  the  free  surface.  They  always  run 
between  the  epithelial  cells,  and  are  connected  into 
anet\Aork.  According  to  some  observers,  they  ter- 
minate w^ith  free  ends,  pointed  or  knobbed  :  but 
according  to  others  these  apparent  free  ends  are 
not  in  reality  free  endings  (Figs.  107,  263  and 
264). 


43  2 


Elemests  of  Histology 


413.  The  nerves  of  Descemet's  membrane  form 
also  a  j^lexus  of  non-medullated  fibres  in  the  posterior 
lavers  of  the  o-round  substance  :  from  them  come 
off  vast  numbers  of  primitive  fibrilla?,  running  a  more 


Fi'^'.  263. — From  a  Horizontal  .Section  through  the  Gokl-stained  Cornea  of 

"  Rabbit ;    the  corneal  (branched)  cells  are  faintly  indicated,  but  the 

nerve  tibrillse  are  well  marked,  also  their  lateral  branchlet.s,  terminating 

apparently  with  a  minute  knob.   {Photograph.  Moderate  magnification.) 

or  less  straight  and  long  course,  crossing  one  another 
often  under  right  angles  :  they  give  off  very  fine 
fibrils,  which  are  closely  associated  with  the  corneal 
corpuscles,  without,  however,  really  becoming  con- 
tinuous wdth  their  protoplasm. 

414.  II.  The  sclerotic  consists  of  lamella?  of 
tendinous  tissue.  The  bundles  of  fibrous  tissue  are 
opaque  as  compared  with  those  of  the  cornea,  although 


SCLEKDl^IC. 


433 


they  pabs  insensibly  into  them.  There  are  lymph 
clelts  bet^veen  the  lamella?  and  trabeculse,  and  in 
them  lie  the  flattened  connective-tissue  corpuscles, 
which,  in  the  dark  eyes  of  some  mammals  only,  contain 


Fig.  264. — From  the  same  preparation  as  in  ijrecediiig  tigiue,  shuwing  tlie 
tine  Nerve  Fibrils  jiassing  along  the  processes  and  bodies  of  the 
branched  corneal  corpuscles.     (Pliotograph.    Moderate  magnification.) 

pigment  granules.      Numerous  elastic  fibrils  are  met 
with  in  the  inner  layers  of  the  sclerotic. 

415.  Between  the  sclerotic  and  choroid  membrane 
is  a  loose  fibrous  tissue,  which  acts  also  as  the  sup- 
jjorting  tissue  for  the  blood-vessels  passing  to  and  from 
the  choroid.  The  part  of  this  loose  tissue  next 
to  the  sclerotic,  and  forming  part,  as  it  were,  of 
the  sclerotic,  contains,  in  dark  eyes  of  mammals, 
numerous  pigmented  connective-tissue  corpuscles ;  it 
c  c 


43+  Elements  of  Histology. 

i«  then  called  lamina  Jusca.  The  rest — i.e.  next 
to  the  choroid  membrane — is  the  supra-choroidal 
tissue. 

416.  There  H re  blood-vessels  in  the  sclerotic,  whicli 
belong  to  it  ;  they  are  arterioles,  capillaries,  and 
veins  :  in  addition  to  these  are  the  vascular  branches 
passing  to  and  from  the  choroid. 

417.  III.  The  li»Jiiii«*iitiii"  pec tiiiatuiii 
iridic  [see  Fig.  262)  is  a  conical  mass  of  spongy  tissue 
joining  hrndy  the  cornea  and  sclerotic  to  the  iris  and 
ciliary  processes.  It  forms  an  intimate  connection,  on 
the  one  hand,  with  the  junction  of  cornea  and  sclerotic, 
and  on  the  other,  withtliat  of  the  iris  and  ciliary  pro- 
cesses. This  ligament  is  composed  of  trabeculse  and 
lamella?  of  stiff  elastic  fibre-,  forming  a  continuity,  on 
the  one  hand,  with  the  lamina  Descemeti  of  the  cornea 
and  the  elastic  fibres  of  the  sclerotic,  and  on  the  other 
with  the  tissue  of  the  ciliary  border  of  the  iris.  The 
trabecular  anastomose,  so  as  to  form  a  honeycombed 
plexus,  and  the  spaces  in  this  plexus  are  lined 
with  a  layer  of  flattened  endothelial  cells,  directly 
continuous  with  the  endothelium  of  Descemet's  mem- 
brane on  the  one  hand,  and  with  the  layer  of  endo- 
thelial cells  covering  the  anterior  surface  of  the  iris 
on  the  other  band.  In  some  mammals,  the  sjiaces 
in  the  ligamentum  pectinatum  near  the  iris  are 
very  considerable,  and  are  called  the  spaces  of 
Fontana. 

The  interlamellar  and  interfascicular  lymph 
spaces  of  the  sclerotic  form  an  intercommunicating 
system. 

The  nerves  form  a  dense  plexus  of  non-medullated 
fibres  in  the  tissue  of  the  sclerotic  (Helfreich). 

At  the  point  of  junction  of  the  cornea  and  sclerotic, 
but  belonging  to  the  latter,  and  in  the  immediate 
neii^hbonrhood  of  the  ligamentum  pectinatum  iridis, 
is  a  circular  canal — the  canal  of   Sclilemni  ;    this  is 


Ciliary  Muscle.  435 

lined  with  (nidotheliuin,  and  is  considered  Ijy  some 
(Schwalbe)  as  a  lymphatic  canal  ;  Ijy  others  (Leljer) 
as  a  venous  vessel. 

418.   IV.   The   <'iliar.v     muscle     (Fig.   2G-J),   or 

tensor  choroideie,  is  tixed  to  this  ligamentum  pecti- 
natum  ;  it  is  composecl  of  bundles  of  non-striped 
muscular  tissue.  This  muscle  consists  of  two  parts  : 
{a)  one  of  circular  bundles  nearest  to  the  iris — this 
is  the  portio  Miilleri ;  {h)  the  greater  part  is  composed 
of  radiating  bundles,  passing  from  the  ligamentum 
pectinatum  in  a  meridional  direction  for  a  consider- 
able distance  backwards  into  the  tissue  of  the  choroid 
membrane.  It  occupies  the  space  between  the  liga- 
mentum pectinatuDi,  sclerotic,  ciliary  processes,  and 
the  adjoining  portion  of  the  choroid  membrane. 
The  bundles  of  the  muscle  are  arranged  more 
or  less  in  lamellpe  ;  within  each  lamella  they  form 
plexuses. 

A  rich  plexus  of  non-medullated  nerve  fibres,  with 
groups  of  ganglion  cells,  belongs  to  the  ciliary  muscle. 


436 


CHAPTER  XXXIX 

IRIS,    CILIARY    PROCESSES    AND    CHOROID. 

419.  I.  The  ii'is  consists  of  the  following  layers  : — 

(1)  The  endothelium  of  the  anterior  surface  :  trans- 
parent, flattened,  or  polyhedral  cells,  each  with  a 
spherical  or  slightly  oval  nucleus  ;  in  dark-coloured 
eyes  of  man  and  mammals  brown  pigment  granules 
are  contained  in  the  cell  substance, 

(2)  A  delicate  hyaline  basement  membrane  :  it  is 
continuous  throucjh  the  trabecule  of  the  lisramentum 
pectinatum  with  the  membrana  Desceraeti  of  the 
cornea. 

(3)  The  substantia  propria  :  this  i-,  the  ground 
substance  ;  it  consists  of  fibrous  connective  tissue  in 
bundles,  accompanying  the  blood-vessels,  which  are 
very  numerous  in  the  tissue  of  the  iris.  Many 
connective-tissue  corpuscles  are  found  in  the  sub- 
stantia propria  :  they  are  more  or  less  branched,  and 
many  of  them  CDntain,  in  all  but  albino  and  blue 
eyes,  yellowish-brown  pigment  granules.  The  depth 
of  the  colour  varies  according  to  the  number  of  these 
pigmented  connective-tissue  cells,  and  to  the  amount 
of  the  pigment  granules  present  in  them. 

(4)  A  hyaline  delicate  basement  membrane  limits 
the  substantia  propria  on  the  ])osterior  surface ;  this 
is  an  elastic  membrane,  and  is  continued  over  the 
ciliary  processes  and  choroid  as  the  lamina  vitrea. 

420.  (5)  The  last  layer  is  the  epithelium  of  the 
posterior  surface  :  this  is  a  layer  of  polyhedral  cells, 
filled  with  dark  pigment  granules,  except  in  albinos, 


JRIS. 


437 


where  there  are  no  pigment  granules       This    enchj- 
theliuiu  is  called  the  uvea,  or  iapetum  nigrum.      The 
interstitial     cement    substiince 
between   the    cells  is    not    pig- 
mented, but  transparent. 

The  name  "uvea"  is  some- 
times applied  to  the  whole  of  the 
iris,  ciliary  processes,  and  choroid 
membrane. 

In  blue  eyes  the  posterior 
epithelium  is  the  only  pigmented 
part  of  the  iris,  and  so  it  is 
also  in  new-born  children,  whose 
iris  appears  blue.  In  all  cases 
where  the  iris  appears  blue, 
this  is  due  to  the  dark  back 
— i.e.  the  pigmented  epithelium 
of  the  posterior  surface — being 
viewed  throutjh  a  dull  layer — 
i.e.  the  substance  of  the  iris. 

421.  Near  the  pupillary 
border  the  posterior  section  of 
the  substantia  propria  contains 
a  broad  layer  of  circular  bundles 
of  non-striped  muscular  tissue  : 
this  is  the  spliincter  pupiUct. 
In  connection  with  this  are 
bundles  of  non-striped  mus- 
cular fibres,  passing  in  a  radi- 
ating direction  towards  the 
ciliary  margin  of  the  iris  :  these 
are  the  bundles  of  the  dila- 
tator pupiUc(;,  forming  a  sort  of 

thin  membrane  near  the  posterior  surface  of  the 
iris  (Henle  and  others).  At  the  ciliary  margin 
the  bundles  take  a  circular  direction  and  form  a 
plexus  (Ivanoff). 


Fi-; 


I  -  vessels 


I  injected)  uf  the  Iris  and 
Choroid  Membrane  of  the 
Eye  of  a  Child.  {Kolliker, 
after  Arnold.) 

a,  Capillaries  of  the  choroid  ; 
b,  era  serrata;  c,  iilood- 
vessels  connected  with,  d, 
those  of  the  ciliary  pro- 
cesses, and  with  e,  those 
of  the  iris;  /,  capillary 
network  of  the  pupillary 
sphincter. 


43^  Elements  of  Histology. 

422.  The  blood-vessels  (Fig.  265)  of  the  iris 
are  very  numerous.  The  arteries  are  derived  from 
the  eirculus  arteriosus  iridis  major,  situated  at  the 
ciliar}"  margin  of  the  iris,  and  from  the  arteries  of 
the  ciliary  processes.  These  arteries  run  in  a  radi- 
ating direction  towards  the  pupillary  margin,  where 
they  terminate  in  a  dense  network  of  capillaries  for 
the  sphincter  pupilla?.  But  there  are  also  numerous 
capillary  blood-vessels  of  a  more  or  less  longitudinal 
direction  near  the  posterior  surface  of  the  iris.  The 
veins  accompany  the  arteries,  and  both  are  situated 
in  the  middle  stratum  of  the  substantia  propria. 

In  the  sheath  of  the  Ijlood -vessels  are  lymplt  clefts 
and  lympli  sinuses;  there  appear  to  be  no  other 
lymphatics. 

423.  The  nerve  fibres  are  very  numerous 
(Arnold,  Formad),  and  in  the  outer  or  ciliary  portion 
of  the  iris  form  a  rich  plexus,  from  which  are  derived  : 
[a)  networks  of  non-medullated  fibres  for  the  dilator 
pupilla3 :  (h)  a  network  of  fine  non-medullated  fibres 
for  the  anterior  surface  ;  and  (c)  a  network  of  non- 
medullated  fibres  for  the  sphincter  pupilhe. 

The  capillary  blood-vessels  are  also  accompanied 
by  fine  nerve  fibres  (A.  Meyer),  and,  according  to 
Faber,  there  exist  ganglion  cells  in  these  nerve  net- 
works. 

424.  TI.  The  miliary  processes  are  similar  in 
structure  to  the  iris,  except,  of  course,  that  they  do 
not  ])0ssess  an  anterior  endothelium  or  an  anterior 
basement  membrane.  The  suhstantia  propria  is 
fibrous  tissue  with  elastic  fibres  and  numerous 
branched  cells,  pigmented  in  dark  (but  not  in  blue) 
eyes.  The  posterior  basement  membrane  is  very 
thick,  and  is  called  the  lamina  vitrea  ;  in  it  may  be 
detected  bundles  of  fine  fibrils.  It  possesses  perma- 
nent folds  arranged  in  a  network  (H.  Muller).  The 
inside  of  it  is  covered  with  a  layer  of  pigmented  poly- 


Ciliary  Processes. 


439 


licdral  v\\\\\\v\\w\\\^W\(^  inpotu))i  nigriDii :  the  cells  are 
polygonal  when  viewed  from  the  surface.  The  in- 
divkliial  cells  are  separated  by  thin  lines  of  a  trans- 
parent cement  substance.  This  pigmented  epithelium 
is    covered  with    a    layer    of   transparent     columnar 


%M 


Y'v^.  2(i(l — Fi-()iii  a  Vertical  Section  thr()uc;li  the  Ciliary  Processes  of  the 
Ox's  Eye.     {Atlas.) 

u.  Fil)roiis  tissue  with  iiigiiiented  cells;  6,  loose  niirons  tissue  fciniiiiiLr  the 
proiier  ineiiihi-ane  of  the  ciliary  process  ;  c.  iiigiiieiited  epithelium  rovermg 
the  posterior  sui-fac-e  of  the  ciliaiy  process;  (/,  epitheloid  cells,  lorniiug  the 
j>ars  ciliaris  rctiiuv  covering  the  l)ai-l\  of  the  ciliary  jirocesses;  e,  Zonula 
Zinnii,  with  laindles  of  lilircs. 

epitheloid  cells,  each  w^ith  an  oval  nucleus.  These  are 
closely  fixed  on  the  tapetum  nigrum,  and  are  the 
continuation  of  the  retina  over  the  ciliary  processes  : 
this  is  thenars  ciliaris  retince  (Fig.  266). 

425.  The  arterial  branches  for  the  ciliary  processes 


440  Elements  of  Histology. 

and  muscle  are  cliieliy  derived  from  the  ciivulus 
arteriosus  iridis  major,  and  fnrn  a  dense  network  of 
capillaries  for  the  former  ;  eacli  ciliar}^  process  pos- 
sesses a  conical  group  of  capillaries  (Fig,  'l^o). 

426.   III.    The     €lioi"oi<l     membrane    consists — 
counting  from   outwards,    i.e.    from  the  sclerotic,  in- 
wards,     i.e.      towards 
.,.'"%•..   ,,-.  the  retina — of  the  fol- 

'^■^^!-0^''  ''^''^0^..  lowing  layers  :^ 

iiii^^^^'.'fi^^^  ^^^^"^^^h^:  ( 1 )   The membrana 

'^0''^''y.!f^^:-'  ■:|M^-%...       "      supra- choroidea.     This 
vi^^^^^j.v^^'^^li^  ..•;jU5:^Sl?^  i'^    ^    Continuation    of 

■^i^-^i}lv^^0^      •••■^'^v;^^''"  the       sclerotic,      with 

which    it    is    identical 

Fjir    -ly^-, — Pimneuted  Connective-tissue       .  ^•, 

"cells  of  the  Choroid  Coat.     (Atlos.^  lU  structure  ;  the  spaCCS 

between  its  lamellae  are 
lined  with  endothelium,  and  represent  lymph  spaces 
(Schwalbe). 

(2)  Next  follows  an  elastic  layer  which  contains 
networks  of  elastic  fibres,  the  branches  of  the  arteries 
and  veins,  and,  in  its  outer  portion,  pigmented  cells 
(Fig.  267). 

427.  (3)  Then  follows  the  membrana  chorio-capil- 
laris,  a  dense  network  of  capillary  blood-vessels  em- 
bedded in  a  tissue  containing  numerous  branched  and 
unbranched  pigmented  and  unpigmented  connective - 
tissue  cells. 

(4)  The  lamina  vitrea  ;  and,  finally, 

(5)  The  tapetum  nigrum,  or  the  pigmented  epithe- 
lium, which,  however,  is  considered  part  of  the  retina. 
In  the  reofion  of  the  ora  serrata  of  the  retina — i.e. 
next  to  the  ciliary  processes — also  this  zone  of  the 
choroidea  is  lined  with  a  layer  of  transparent, 
columnar,  epitheloid  cells,  representing  the  jDars 
ciliaris  retinte. 

428.  The  arteriae  ciliares  breves  and  recurrentes, 
situated  in  the  outer  part  of  the  choroidal  tissue,  form 


Choroip.  441 

iiltiniatcly  tlx'  tlciisc  networks  of  capillaries  fof  the 
cliorio-capillai-ies.  The  veins  derived  from  this  pass 
into  the  outer  part  of  the  choroid,  where  they  anasto- 
mose so  as  to  form  the  peculiar  large  veins,  which  are 
called  the  vente  vorticosse. 

In  the  eyes  of  some  animils  (cat,  dog,  sheep,  ox) 
there  exists  a  special  layer  of  cells  (cat,  dog)  or 
fibres  (herbivora),  which,  owing  to  its  capability  of 
reflecting  a  great  deal  of  light,  is  called  the  tapetum 
hicidnm  or  me  iibrana  versicolor  of  Fielding.  This 
layer  when  present  is  situated  between  the  stroma 
of  the  choroid  (laver  2)  and  the  membrana  chorio- 
capillaris  (layer  3). 


442 


CHAPTER  XL. 

THE  LENS  AND  VITREOUS  BODY. 

429.  (1)  TIk*  lens  consists  of  a  thick,  firm,  elastic 
capsule  and  of  the  lens  substance.  The  former  shows 
fine  longitudinal  strijB,  and  diminishes  in  thickness 
towards  the  posterior  pole  of  the  lens.  The  surface 
of  the  capsule  facing  the  anterior  surface  of  the  lens 
substance  is  lined  with  a  single  layer  of  pol^^hedral, 
granular-looking,  epithelial  cells,  each  with  a  spherical 
or  oval  nucleus.  This  epithelium  stops  as  such  at  the 
margin  of  the  lens,  where  its  cells,  gradualh'^  elongat- 
ing, pass  into  the  lens  fibres.  The  nuclei  of  these  lie 
in  a  curved  plane  belonging  to  the  anterior  half  of  the 
lens :  this  is  the  nuclear  zone.  The  lens  substance 
consists  of  the  lens  fibres.  These  are  band-like,  hexa- 
gonal in  transverse  section  ;  their  outline  is  beset  with 
numerous  fine  ridges  and  furrows,  which  in  neigh- 
bouring fibres,  fitting  the  one  into  the  other,  form  a 
firm  connection  between  the  fibres  (Valentin,  Henle, 
Kolliker,  and  others).  The  fibres  of  the  peripheral 
portion  are  broader  and  thicker,  and  their  substance 
is  less  firm  than  those  of  the  centre — i.e.  of  the  lens 
nucleus.  The  substance  of  the  lens  fibres  is  finely 
granular  and  delicately  and  longitudinally  striated. 

430.  The  lens  fibres  (Fig.  268)  are  arranged  in 
concentric  lamelLie,  each  consisting  of  a  single  layer  of 
fibres  joined  by  their  broad  surfaces.  Each  fibre  is 
slightly  enlarged  at  the  extremities ;  and  in  each 
lamella  the  fibres  extend  from  the  anterior  to  the 
posterior   surface.      Their   extremities   are  in  contact 


ViTRF.ous  Body. 


443 


with  the  ends  of  the  fibres  of  the  sjinie  lamelhi  in  tlie 
siUiires,  or  the  rays  of  the  so-called  lens  stars.  In 
the  lens  of  the  newly-born  child,  the  stars  of  both 
anterior  and  ])Osterior  lamellae  possess  three  such  rays, 
while  in  the  adidt  each  of  these  rays  has  secondary 
rays.  Tn  these  rays  there  is  a  homogeneous  thin  layer 
of  an  albuminous  cement  substance  ;  a  similar  sub- 
stance in  minute  quantity  is  also  present  between  the 
lamellve,  and  in  it  occur  smaller  or  larger  clefts  and 
channels,  which  evidently  carry  the  nutritious  fluid  for 
the  lens  fibres. 

431.  (:2)  The  vitreous  bo<ly  is  a  fluid  substance 
enclosed  in  a  delicate  hyaline  capsule — the  memhrana 
hyaloidea.      This   membrane,  at 

tlie  margin  of  the  fossa  patel- 
la ris  of  the  vitreous  body — i.e. 
the  fossa  in  wliich  the  lens  is 
lodged — and  without  covering 
this  fossa,  passes  as  the  zonula 
ciliaris,  or  zonula  Zinnii,  or 
suspensory  ligament  of  the  lens, 
to  tlie  margin  of  the  latter,  to 
whicli  it  is  firmly  adhering.  So 
it  adheres  also  to  the  surface  of 
the  ciliary  processes.  The  zonula 
Zinnii  is  hyaline  and  firm,  and 
is  strentjthened  bv  numbers  of 
bundles  of  minute  stifl'  fibrils. 

Between  the  suspensoi  y  liga- 
ment of  the  lens,  the  margin  of  the  lens  and  of  the 
fossa  patellaiis  is  a  circular  lymph  space,  called  the 
canalis  Petiti. 

Beneath  tlie  membrana  hyaloidea  are  found  iso- 
lated nucleated  granular-looking  cells  (the  sub-hyaloid 
cells  of  Ciaccio),  possessed  of  amoeboid  movement 
(Ivanofl). 

432.  The  substance  of  the  corpus  vitreum  appears 


i  ,:^'^>)^j  ■^^)/  A jj^  -  - 


Fig.  2(iS. — From  a  Section 
through  the  Lens  of  Dog. 
(Atlus.) 

Sliciwing  four  lamellse  ;  in 
each  the  component  lens 
filires  are  cut  across  ;  they 
appear  as  flattened  hexa"- 
u'ons. 


444  Elements  of  Histot.ogy 

didereiitiuted  by  clefts,  conct-ntric  in  the  })Hripberal, 
radiating  in  the  central  part  (Briicke,  Hannover, 
Bowman,  Ivanoff,  Schwalbe).  But  these  do  not  con- 
tain an}'  distinct  membranous  structures  (Stilling, 
IvanofF,  Schwalbe). 

The  canalis  hyaloideus,  or  canal  of  Stilling,  extends 
from  the  papilla  nervi  optici  to  the  posterior  capsule 
of  the  lens,  and  is  lined  with  a  continuation  of  the 
membrana  hyaloidea. 

433.  In  the  substance  of  the  corpus  vitreum  occur 
isolated  nucleated  cells,  possessed  of  amoeboid  move- 
ments, and  some  contain  vacuoles,  indicating  com- 
mencinjj  desfeneration.  Thev  are  all  identical  with 
white  blood-corpuscles  (Lieberklihn,  Schwalbe). 

Fine  V)undles  of  fibrils  are  occasionally  seen  in  the 
substance  of  the  vitreous  body. 


445 


CHAPTER   XLT. 


THE    RETINA. 


±iJj±ULH 


SMAlAAl~---{ 


-A 


434.  The  retina  (Fig.  269)  consists  of  the  follow- 
ing layers,  counting  from  inwards  towards  the  choroid 
membrane  :  —  (1) 
The  membrana  li- 
mit ans  interna, 
wliich  is  next  to 
the  membrana  hya- 
loidea  of  the  vi- 
treous body ;  (2) 
the  nerve  fibre 
layer  ;  (3)  the  layer 
of  c(anglion  cells  ; 
(4)  the  inner  gi-an- 
ular  or  inner  mole- 
cular layer  ;  (5)  the 
layer  of  inner 
nuclei ;  (6)  the 
outer  granular,  or 
outer  molecular,  or 
internuclear  layer  : 
(7)  the  layer  of 
outer  nuclei;  (8) 
th  e  m  em  br  ana 
limitans  externa ; 
(9)  the  layer  of 
rods  and  cones ; 
and  (10)  the  pig- 
mented epithelium  of  the  retina,  or  the  tapetum 
nigrum  mentioned  above  (p.  439),  which  forms,  at  the 


^    ,-  o  . 
;  o  0  oo 


o  ^3  Oa 
3  3  o  a  tt_ 


5-— 771 


Fi<r.  269. — From  a  Transverse  Section  through 
tlie  Eye  of  Sheep ;  peripheral  portion  of 
retina.     (Atlas.) 

a.  Inner  parr  of  sclerotic ;  b,  supra-choroidal 
Cpigmeiited)  lamellse;  c,  d.  layers  of  choroid 
C'lat;  e.  pigmented  epithelium  of  retina;  /, 
hiyer  of  rods  ;  jr,  cones  ;  7i,  layer  of  outer  nuclei ; 
i," outer  molecular  layer;  j,  layer  of  inner 
nuclei ;  k.  inner  molecular  layer ;  I,  layer  of 
Kanglion  cells,  •with  the  radial  or  Muller's 
fibres  between  ;  jh,  layer  of  nerve  fibres. 


446 


Elemexts  of  Histology. 


same  time,  the  inner  lining  epithelium  of  the  choi-oid 
membrane. 

435.   From  this  arranixement  are  excepted  (n)  the 


mm. 

\-J}      f-fC-,   ^r    ^    ; 


Fig.  270.— Diagram  of  the  Ner-    Fi^ 
voiis  Elements  of  the  Retina. 


•271.— Diagram   of  the    Connective- 
Tissue  Substance  of  the  same. 


«    xro,.-<>  fihrps  ■  1    •'in^'lion  ceUs:4,  inner  molecular  layer;  5.   inner  nuclear 
-  ';lver:^6.omermole6u^rl^y^    riourernuclearlaver ;  8.  membranahmitans 
externa ;  9,  rods  and  cones.    (Jfojc  Schultze.) 

papiUa  nervi  optici,  (b)  the  macula  lutea  and  fovea 

centralis  retinae,  and  (c)  the  ora  serrata  of  the  retina. 

(a)  The  papilla  nervi  optici,  or  the  blind  spot  of 


Retina.  447 

the  retina,  represents  the  entrance  of  tlie  optic  nerve 
fibres  into  the  retina;  thence,  as  from  a  centie,  they 
spread  out  in  a  radiating  direction  into  the  sancer- 
sliaped  retina,  of  which  they  form  the  internal  layer. 
No  other  elements  of  the  retina  are  present  at  the 
papilla,  except  a  continuation  of  the  limitans  interna. 
At  the  papilla  nervi  optici  the  arteria  and  vena 
centralis  nervi  optici  also  enter,  and  spread  out  with 
their  branches  in  the  inner  layers  of  the  retina.  A 
large  lymph  space  is  also  found  there. 

(6)  The  macula  lutea  and  fovea  centralis  will  be 
considered  after  the  various  layers  of  the  retina  have 
been  described. 

(c)  At  the  ora  serrata  all  circular  and  nuclear 
elements  of  the  retina — except  the  pigmented  epithe- 
lium— and  the  nerve  fibres,  come  to  an  end  ;  but  the 
limitans  interna,  with  its  peculiar  radial  or  Miiller's 
fibres,  is  continued  over  the  ciliary  processes  in  the 
shape  of  columnar  epitheloid  nucleated  cells  men- 
tioned above  :  this  is  the  pars  ciliaris  retime. 

436.  Structure  of  the  layers  of  the  retina  (Figs. 
270,  271). 

(1)  The  iiieiiibraiia  liiiiitaii!^  iiiteriia  is 
composed  of  more  or  less  }jolygonal  areas,  which  are 
the  ends  or  bases  of  pyramidal,  finely-striated  fibres 
— the  radial  fibres  of  JlilUer.  Each  radial  fibre  passes 
from  the  limitans  interna  in  a  vertical  direction 
through  all  lavers  to  the  limitans  externa,  and  on  its 
way  gives  off  numerous  lateral  branchlets,  fibrils  and 
membranes,  which  anastomose  with  one  another  so  as 
to  form  a  honeycombed  stroma  or  matrix  for  all 
cellular  and  nuclear  elements  of  the  retinal  layers. 
In  the  nerve  fibre  layer  the  radial  fibres  are  thickest, 
this  being,  in  fact,  the  pyramidal  basis  ;  in  the  inner 
nuclear  layer  each  possesses  an  oval  nucleus. 

437.  (2)  The  layer  ol  nerve  fibres. — The 
optic  nerve  fibres  at  their  entrance  into  the  eyeball 


448 


Elements  of  Histology. 


lose  their  medullary  sheath,  and  only  the  transparent 
axis  cylinder  is  prolonged  into  the  retina.  In  man, 
medullated  nerve  fibres  in  the  retina  are  very  excep- 
tional :  in  the  rabbit  there  are  two  bundles,  whose 
libres  retain    their  medullary  sheath    in     the    retina 


Fk 


jectiou    of   Retina    of    Dog.     \\Aflei 
"  Anatomy.") 


Cajal,    from    Quain's 


u.  Cone  rtbre  ;  h,  rod  fibre  aud  nucleus  ;  c,  d,  bipolar  cells  ■with  inner  nuclei,  with 
vertical  ramifications  to  receive  the  knobbed  ends  of  the  rod  fibres,  e,f,  with 
flattened  ramifications  for  the  arborising  ends  of  the  cone  fibres  ;  g.  gan- 
glion cell  sending  an  axon  to  the  outer  molecular  layer;  /),  spongioblast ; 
1,  nerve  fibres  passing  to  the  outer  molecular  layer  ;],  centrifugal  nerve  fibres 
passing  into,  and  terminating  in,  inner  molecular  layer  :  m,  nerve  fibres 
passing  toinner  molecular  layer ;  n,  ganglion  cells  ;  a,  outer  molecular  layer; 
B,  inner  molecular  layer;  c,  nerve  fibre  layer. 

(Bowman).  The  nerve  fibres  remain  grouped  in 
bundles  in  the  retina,  and  even  form  plexuses.  For 
obvious  reasons,  the  number  of  nerve  libres  in  the 
nerve  fibre  lay^n*  diminishes  towards  the  ora  serrata. 

438.  (3)  Tlie  layer  of  g^sin^l ion  cells. — There 
is  one  stratum  of  these  cells  only,  except  in  the 
macula  lutea,  where  they  form  several  strata.      Each 


Retina. 


449 


cell  is  multipolar,  and  possessed  of  a  lar^e  nucleus. 
One  process  is  directed  inwards  and  Ijeconies  the 
axon,  being  a  fibie  of  the  nerve  fibre  layer.  Several 
branched  processes  or  dendrites  pass  from  the  opposite 
side  of  the  cell  into  the  next  outer  layer — i.e.  the 
inner  molecular  layer. 

From  the  researches  of  Eamon  y  Cajal,  it  is  clear 


Fig.273. — From  the  Retina  of  Dog.  i^Afttr  Ca}al,fTom  Quaiiis  ''Anatomy. 

A,  Small  amacrine  (spougiuhlast)  of  the  inner  molecular  layer :  c,  large  ganglion 
cell ;  /,g,h,  i,  small  ganglion  cells  arborising  in  the  inner  molecular  layer. 


that  the  dendrites  terminate  by  arborisations  or  den- 
drons  in  the  next  or  inner  molecular  layer  (see  Figs. 
L'72,  27:3,   and  274). 

The  ganglion  ceils  are  separated  from  one  another 
by  the  radial  fibres  of  Miiller. 

439.  (4)  The  inner  nioleciilai'  layer  is  a 
fine  and  dense  reticulum  of  fibrils,  with  a  small 
amount  of  granular  matter  between.  The  fibrils  are 
connected  with  lateral  branchlets  of  the  radial  fibres 
of  ^luller.  This  layer  is,  on  account  of  its  thickness, 
a  conspicuous  part  of  the  retina.  In  lower  vertebrates 
it  a])pears  stratified. 

As  mentioned  just  now,  it  contains  the  terminal 
arborisations  of  the  dendrites   of  the  ganglion  cells. 

440.  (5)  The  inner  nnrlear  layer  contains  in 
a  honeycombed  matrix  of  a  hyaline  stroma  numerous 
nuclei,  in  two.  three,  or  four  layers.  In  the  am- 
phibian retina  these  form  a  larger  number  of  layers. 
Some  oblong  nuclei  of  this  layer  belong,  as  has  been 
mentioned    above,    to  the    radial    fibres    of    Miiller. 

D  D 


45° 


Elements  of  Histology 


Js^ext  to  the  molecular  layer  are  small  nuclei  belonging 
to  flattened  branched  cells  (Vintschgau).  the  spongio- 
hh.sts  of  W.  Miiller.  These  cells  have  been  shown 
by  Golgi's  method  to  be  possessed  of  rich  arborisations, 
^vhich  extend  horizontallv  into   the  outer   and  inner 


Fig.  274— Section  of  Retina  of  Bird.  {After  Cajal,/rom  (^uain's  ^'Anatomy."\ 

A,  B.  Large  sponsioljlasts  of  inner  nuclear  layer;  c.  small  spongioblast;  d. 
bipolar  cell  of  inner  nuclear  layer  wirh  a  and  b  arborising  in  inner  mole- 
cular layer  and  also  terminating  at  k  at  the  limitans  externa ;  f,  g,  rod  and 
cone  nuclei ;  H,  i,  cells  with  arborisations  in  outer  molecular  layer ;  j,  radial 
fibre  of  Muiler. 


molecular  layers  (see  Fig.  272).  Ramon  y  Cajal 
desicrnates  them  as  amacrines.  But  the  ofreat 
majority  of  the  nuclei  of  this  layer  are  slightly  oval, 
with  a  reticulum  in  their  interior.  Each  belongs  to 
a  spindle-shaped  cell,  with  a  small  amount  of  proto- 
plasm around  the  nucleus  :  it  is,   in   fact,    a  bipolar 


Retina.  451 

ganglion  cell  (Max  Scliultze),  of  which  ono  i)rocess  (the 
innei")  ))asses  as  a  fine  varicose  fibre  into  the  inner 
molecular  layer,  where  it  terminates  as  a  delicate  den- 
dron,  while  the  other  or  outer  process  passes  into  the 
next  outer  layer  of  the  retina — i.e.  the  outer  molecu- 
lar layer,  to  terminate  here  by  a  rich  arborisation  or 
dendron  (Fig.  272). 

(6)  Tlie  outer  iiiolenilai*  layer  is  of  the  same 
structure  as  the  inner  molecular  layer- — i.e.  a  fine 
reticulum  of  fibrils — but  is  considerably  tliinner  than 
the  latter.  It  also  contains  the  dendrons  of  cells 
inside  and  outside  it  (Fig.  272). 

441.  (7)  The  outer  uuclear  layer  contains,  in 
a  honeycombed  matrix,  a  large  number  of  oval  nuclei. 
In  the  retina  of  man  and  mammals  these  nuclei  are 
always  present  in  considerably  greater  numbers  or 
layers  than  those  of  the  inner  nuclear  layer,  but  in 
the  amphibian  animals  the  reverse  is  the  case.  They 
are  smaller  than  the  nuclei  of  the  inner  nuclear  layer, 
and  show  often  a  peculiar  trans^'ersely-ribbed  differ- 
entiation of  their  contents  (Henle,  Krause).  The 
honeycombed  matrix  of  this  layer  is  in  connection 
with  lateral  branchlets  of  the  radial  fibres  of  Miiller, 
with  which  it  forms  a  sort  of  limiting  delicate  mem- 
brana  propria  at  the  outer  surface  of  the  layer; 
this  is 

442.  (8)  The  liuiltaus  externa — The  nuclei  of 
the  outer  nuclear  layer  next  to  this  limitans  externa  are 
connected,  in  the  retina  of  man  and  mammals,  with 
the  cones,  while  the  nuclei  farther  inwards  from  the 
limitans  externa  are  connected  with  the  rods.  In 
both  instances  the  connection  is  established  throuorh 
holes  in  the  limitans  externa.  Each  nucleus  of 
the  outer  nucleai-  layer  is,  in  reality,  that  of  a 
spindle-shaped  cell  with  a  minute  amount  of  proto- 
plasm ;  this  is  prolonged  outwards,  as  the  outer  part 
of  the  rod-  or  cone-fibre,  to  become  connected  with  a 


452  Elements  of  Histology. 

rod  or  cone  respectively,  while  inwards  it  passes  into 
a  longer,  more  conspicuous  fibre,  the  inner  part  of  the 
rod-  or  cone-fibre  (Fi,cj.  272).  According  to  Ramon 
y  Cajal,  the  cone-fibre  terminates  as  a  flat  dendron 
in  contact  witli  the  tufty  arborisation  of  the  outer 
process  of  the  cells  of  the  inner  nuclear  layer— f  6".  in 
the  outer  molecular  layer  :  the  rod-fibre  on  the  other 
hand  terminates  in  the  outer  moleculai-  layer  as  a 
small  knob  (Fig.  272)  in  tlie  outer  dendron  of  the 
same  cells 

443.  (*.))  The  rods  and  cones. — Each  rod  is 
of  cylindrical  shape,  Avith  rounded  or  conical  outer 
extremity  :  it  con.sists  of  an  outer  and  inner  member, 
joined  by  linear  cement.  Its  substance  is  bright  and 
glistening,  and  that  of  the  outer  member  is  composed 
of  the  neurokeratin  of  Kiihne  and  E^vald.  In  the 
fresh  state  the  outer  member  shows  a  more  or  less  fine 
and  longitudinal  striation,  due  to  longitudinal  fine 
ridges  and  furrows  (Hensen,  Max  8chultze).  After 
certain  reagents,  such  as  serum,  liquor  potass^e,  the  outer 
rod-member  disintegrates  into  numerous  transverse, 
thin,  homogeneous-looking  discs  (Hannover).  The 
inner  member  in  tlie  human  rods  is  slightly  broader 
than  the  outer  :  it  is  pale  or  tinely  and  longitudinally 
striated,  and  contains  in  many  instances  a  peculiar 
lenticular  structtire  :  in  the  human  and  mammalian 
retina  this  is  aljsent.  but  in  its  stead  is  a  mass  of 
lono-ittidinal  fibrils  (^fax  ►"^cliultze).  The  inner  member 
passes  through  a  hole  in  the  limitans  externa,  and 
becoming  thiniif-r.  represents  the  outer  part  of  the 
rod -fibre. 

4-4-1:.  Each  cone  is  composed  of  an  outer,  short, 
pointed,  conical  member,  and  an  inner  larger  member 
with  convex  surface  :  this  is  the  hody  of  the  cone. 
The  outer  member  of  the  cone  separates  under  certain 
conditions  also  into  thin  transverse  discs.  The  body 
of  the  cone  is  longitudinally  and  finely  striated.     The 


Rktina. 


453 


outer  extremity  of  tlic  body 
birds,  reptiles,  and  amphibia 
contains  a  spherical  corpuscle 
of  red,  orange,  yellow,  green, 
or  even  Ijlue  colouration. 

The  cones  are  shorter  than 
the  rods,  the  pointed  end  of 
the  former  not  reaching  much 
farther  than  the  junction  be- 
tween the  outer  and  inner 
members  of  the  rods. 

In  the  macula  lutea  and 
fovea  centralis  of  man  and 
most  mammals  there  are  pre- 
sent cones  only,  and  towards 
the  peripheral  portion  of  the 
retina  they  gradually  decrease 
in  numbers  ;  in  the  peripheral 
part  there  are  only  rods.  But 
in  birds  the  cones  exceed  the 
rods  everywhere. 

In  the  bat  and  mole  the 
macula  lutea  possesses  no 
cones,  and  in  the  owl,  rat, 
mouse,  guinea-pig  and  rabbit 
they  are  few  and  small. 

445.  The  outer  members 
of  the  rods  (only)  show  in 
the  fresh  and  living  state  a 
peculiar  ditiuse  purplish  colour 
(Leydig,  Boll,  Kiihne)  :  this  is 
the  visual  purple  or  Rhodopsin 
of  Kiihne.  When  exposed  to 
sunlight  it  passes  through 
red,  orange,  and  yellow,  and 
finally  disappears  altogether 
— becomes  bleached.    There  is 


of  the  cones  in   many 


Fig.  275. — Vertical  Section 
through  Ketiiia  of  Frog. 
(Atlas.) 

a.  Pigmented  epitbeliiim  of 
retina  or  tapetum  nigrum; 
5,  outer  nieml>ers  of  rods, 
those  of  cones  l)etween  them  ; 
c,  inner  mem  tiers  of  rods  and 
cones;  d,  liniitaus  externa; 
e,  outer  nuclei ;/,  outer  mole- 
cular layer  ;  </,  inner  nuclei ; 
/(,  inner  molecular  layer ;  i, 
nuclei  of  ganglion  cells;  j, 
nerve  fibres;  the  pyramidal 
extremities  of  the  radial 
fibres  arc  well  shown. 


454  Elements  of  Histology. 

no  visual  purple  in  tlie  rods  of  Rhinolophus  hipposi- 
deros,  fowl  and  pige  )n  :  in  those  retinae  in  which  the 
cones  contain  coloured  globides  {ses  above)  the  sur- 
rounding rods  are  wanting  in  the  visual  purple. 

The  visual  purple  stands  in  an  intimate  relation  to 
the  pigmented  epithelium  of  the  retina,  since  a  retina 
regains  its  visual  purple  after  bleaching,  when  replaced 
on  the  pigmented  epithelium  (Kiihne).  This  holds 
good,  of  course,  onlv  within  certain  limits. 

•446.  (10)  The  pij?iiiL'iite<l  epitlieliiiiii  (Fig. 
275),  or  tapetum  nigrum,  is  composed  of  polygonal 
protoplasmic  cells,  which,  when  viewed  from  the 
surface,  appear  as  a  mosaic,  in  which  they  are 
separated  from  one  another  by  a  thin  layer  of  cement 
substance.  Eacli  cell  shows  an  outer  non-pigmented 
part,  containing  the  slightly  flattened  oval  nucleus, 
and  an  inner  part  next  to  the  rods  and  cones, 
which  is  full  of  pigmented  crystalline  rods 
(Frisch).  Tliis  part  is  prolonged  into  numerous 
tine  fibrils,  each  containing  a  row  of  the  pig- 
mented particles,  and  these  fibrils  pass  between  the 
outer  members  of  the  rods,  to  which  they  closely 
adhere,  and  which  in  reality  become  almost  entirely 
ensheathed  in  them  (M.  Schultze).  Each  cell  supplies 
a  number  of  rods  with  these  fibrils.  Sunlight  causes 
a  protrusion  of  these  fibrils  from  the  cell  body,  whereas 
in  the  dark  they  are  retracted  (Kiihne),  in  a  manner 
similar  to  what  takes  place  in  pigmented  connective- 
tissue  cells.  {See  par.  43.)  The  tint  of  this  pigment 
is  darker  in  dark  than  in  light  eyes.  It  is  bleached 
by  the  light  in  the  presence  of  oxygen  (Kiihne),  but  it 
persists  in  the  absence  of  oxygen  ( Mays ). 

447.  The  macula  lutea  (Fig.  276)  of  man  and 
ape  contains  a  diffuse  yellow  pigment,  between  the 
elements  of  the  retina  (M.  Schultze).  In  man  and 
most  mammals,  as  mentioned  above,  there  are 
hardly    any    rods    here,    but    cones    only ;  these    are 


Retina. 


455 


longer  than  in  other  parts,  and  in  the  fovea  centralis 
tliey  are  longest,  and,  at  the  same  time,  very  thin. 
Since  there  are  only  cones  here,  the  nuclei  of  the 
outer  nuclear  laj^er  are  limited  to  a  very  few  layers 
(generally  about  two)  next  to  the  membrana  limitans 


Fig.  276. — From  a  Vertical  Section  through  the  Macula  lutea  and  Fovea 
centralis.     (Diagram  by  Max  Schultze.) 

a.  Nerve  fibre* :  b,  ganarlion  cells ;  c.  Inner  molecular  layer :  d,  inner  nuclei ; 
e,  outer  molecular  layer ;  /,  coue-flbres  with  their  outer  nuclei ;  g,  cones. 


externa.  For  this  reason,  the  rest  of  the  outer  nuclear 
layer  is  occupied  by  the  cone-Hbres  only,  which  in  the 
fovea  centralis  pass  in  a  slanting,  or  almost  horizontal, 
direction  sideways  into  the  outer  molecular  layer.  The 
ganglion  cells  fi)rm  several  strata  in  the  macula  lutea. 
In  the  fovea  centralis  are  present  the  cones  (very  long 
and  thin),  the  limitans  externa,  the  few  nuclei  repre- 
senting the  outer  nuclear  laj^er,  a  thin  continuation  of 
the  inner  molecular  layer,  and  the  limitans  interna. 
448.   In   the   embryo,   the    primary    optic    vesicle 


456  Elements  of  Histology. 

becomes  invaginated  so  as  to  form  the  optic  cup, 
which  consists  of  two  layers — an  outer,  giving  origin 
to  the  pigmented  epithehum  :  and  an  inner,  the  retina 
proper.  In  this  Jatter  the  rods  and  cones,  with  their 
hbres  and  the  nuclei  of  the  outer  nuclear  layer,  are 
represented  by  columnar  epithelial  cells  (the  sensory 
epitlieJium),  while  all  the  other  layers — i.e.  the  outer 
molecular,  inner  nuclear,  inner  molecular  layer,  gan- 
glion cells,  nerve  fibres,  and  limitans  interna — are  re- 
presented by  a  separate  layer  :  Briickes tunica nervea 
or  Henle's  stratum  nerveum. 

449.  The  blood-vessels  of  the  retina.  The 
branches  of  the  arteria  and  vena  centralis  of  the  optic 
nerve  can  be  traced  into  the  retina  in  the  layer  of 
nerve  fibres  and  ganglion  cells,  while  the  capillaries 
connecting  the  arteries  with  the  veins  extend  as  far  as 
the  outer  molecular  layer. 

The  lyiiipliatics  of  the  retina  exist  as  perivas- 
cular lymphatics  of  the  retinal  veins  and  capillaries 
(His).  Lymph  channels  are  present  in  the  ner\e  fibre 
layer. 

450.  The  lamina  eribrosa  is  the  part  of  the 
sclerotic  and  choroid  membrane  through  which  the 
optic  nerve  filires  have  to  pass  in  order  to  reach  the 
papilla  nervi  optici.  In  the  optic  nerve  the  fibres  are 
grouped  in  larger  or  smaller  groups  — not  bundles  in 
the  sense  of  those  present  in  other  nerves  and  sur- 
rounded by  perineurium  {see  Chapter  XI Y.)  ;  these 
groups  are  surrounded  by  septa  of  connective  tissue, 
^nd  they  pass  through  corresponding  holes  of  the 
sclerotic  and  choroid. 

451.  The  optie  nerve  possesses  three  sheaths, 
composed  of  fibrous  connective  tissue  :  an  outer,  or 
dural  :  a  middle,  or  arachnoidal  ;  and  an  inner,  or 
pial,  sheath  — all  continuations  of  the  membranes  of 
the  brain.  The  pial  sheath  is  the  perineurium,  the 
optic  nerve  being  comparable  to  a  compound  nerve- 


Retina.  457 

bundle  {see  Chapter  XIY.).  The  dural  slieath  of 
the  optic  nerve,  at  its  entrance  into  the  lamina 
cribrosa,  jiasses  into  the  outer  strata  of  the  sclerotic, 
while  the  arachnoidal  and  pial  sheaths  pass  into  the 
inner  strata  of  the  sclerotic.  Outside  the  dural  sheath 
is  a  lymph  space— the  supravaginal  sj>ace  :  and  also 
between  these  various  sheaths  are  lymph  spaces — the 
subdural  or  sub  vaginal  space  of  Schwalbe,  and  the 
subarachnoidal  space.  The  supravaginal  and  suit- 
vaginal  spaces  anastomose  with  one  another  (Michel). 
452.  Around  the  sclerotic  is  a  lymph  space  limited 
bv  a  tiVji'ous  membrane — the  Tenonian  co.ps.ii.le  :  the 
space  is  called  tlie  Tenonian  space.  The  supravaginal 
space  anastomoses  with  this  Tenonian  space,  and  into 
it  pass  also  the  lymph  clefts  in  the  suprachoroidal 
tissue  (Schwalbe),  by  means  of  the  lymph  canalicular 
system  of  the  sclerotic  (Waldeyer).  The  snpra- 
choroidal  lymph  spaces  communicate  also  with  the 
subarachnoidal  space  of  the  optic  nerve. 


458 


CHAPTER    XLII. 

THE    OUTER    AXD    MIDDLE    EAR. 

453.  The  meatus  auditorius  externus  is  lined  with 
a  delicate  skin,  in  structure  identical  with,  but  thinner 
than,  the  skin  of  other  parts.  The  ceruminous 
glands  have  been  mentioned  and  described  before. 
The  cartilage  of  the  auricula  and  its  continuation  into 
the  meatus  auditorius  externus  is  elastic  cartilage. 

454.  The  in  em  bran  a  tyinpani  sej^arating  the 
outer  from  the  middle  ear  has  for  its  matrix  a  firm 
stratum  of  stiff  trabecuhe  of  fibrous  connective  tissue, 
with  numerous  elastic  fibrils  and  elastic  membranes. 
This  is  the  middle  and  chief  stratum  of  the  membrane  : 
outwards  it  is  covered  with  a  delicate  continuation  of 
the  skin  of  the  meatus  auditorius  externus,  and  inwards 
M'ith  a  continuation  of  the  delicate  mucous  membrane 
lining  the  cavum  tympani.  In  the  middle  stratum  of 
the  membrana  tympani  the  trabecule^  radiate  more  or 
less  from  the  junction  of  the  manubrium  mallei  with 
the  membrane  ;  but  towards  the  periphery  many  are 
also  arranged  in  a  circular  direction.  The  former 
belong  to  the  outer,  the  latter  to  the  inner,  portion  of 
the  middle  stratum. 

The  mucous  membrane  lining  the  tympanic  surface 
of  the  memljrane  is  delicate  connective  tissue,  covered 
with  a  single  layer  of  polyhedral  epithelial  cells. 

The  blood-vessels  form  capillary  networks  for  all 
three  layers — i.e.  a  special  network  for  the  skin  layer, 
a  second  for  the  middle  stratum,  and  a  third  one  for 
the  mucous  layer ;  the  lymphatics  are  also  arranged  in 


Outer  and  Mmni.E  Ear.  459 

this  way.  An  intercommunicating  system  of  lym- 
phatic sinuses  and  ck^fts  (Kessel)  is  left  between  tlie 
trabeculiu.  The  non-medullated  nerve  fibres  form 
plexuses  for  the  skin  and  mucous  layer ;  from  these 
pass  ott'  fine  fibrils,  which  form  a  sub-epithelial  net- 
work, and  from  this  the  tilji'ils  pass  into  the  epithelium. 

455.  The  tuba  E:ii«itsicliii  is  lined  with  a 
uuicous  meml)rane,  which  is  a  continuation  of  that 
lining  the  upper  part  of  the  phar^'nx,  and  therefore, 
like  it,  is  covered  on  its  inner  or  free  surface  with 
columnar  ciliated  epithelium.  As  in  the  pharynx,  so 
also  here,  we  find  a  good  deal  of  adenoid  tissue  in  the 
mucous  membrane. 

The  cartilage  of  the  tuba  Eustachii  in  the  adult 
approaches  in  structure  the  elastic  cartilages  of  other 
parts. 

456.  The  caviiiii  tympaiii,  including  the  cellulte 
mastoidese  and  the  surface  of  the  ossicula  auditus,  is 
lined  with  a  delicate  connective-tissue  membrane.  Its 
free  surface  is  covered  with  a  single  layer  of  poly- 
hedral epithelial  cells  in  the  following  regions  :  on 
the  promontory  of  the  inner  wall  of  the  cavity,  on  the 
ossicula  auditus,  on  the  roof  of  the  cavity,  and  in  the 
cellulae  mastoidea3 ;  in  all  other  parts  it  is  columnar  cili- 
ated epithelium,  like  that  lining  the  tuba  Eustachii. 

457.  The  three  ossicula  auditus  are  osseous 
substance  covered  with  periosteum,  which  is  covered 
with  the  delicate  mucosa  just  described.  The  liga- 
ments of  the  bones  are,  like  other  ligaments,  made  up 
of  straight  and  parallel  bundles  of  tiV)rous  connective 
tissue.  The  articulation  surface  of  the  head  of  the 
malleus,  of  the  incus,  of  the  extremity  of  the  long 
process  of  the  incus,  and  of  the  stapes,  are  covered 
with  hyaline  (articular)  cartilage. 


460 


CHAPTER    XLTII. 

THE     INTERNAL     E  A  K. 

458.  The  osseous  labyrinth  consists  of  the  vesti- 
bule, prolonged  on  one  side  into  the  cochlea,  and  on 
the  other  into  the  three  semicircular  canals,  each  of 
which  possesses  an  am^^ulla  at  one  extremity.  The 
vestibule  shows  two  divisions — the  fovea  hemispherica 
next  to  the  cochlea,  and  the  fovea  hemi-elliptica  next 
to  the  semicircular  canals.  The  cochlea  consists  of 
two  and  a  half  turnings  twisted  round  a  bony  axis — the 
modiolus.  From  this  a  bony  lamina  extends  towards 
the  outer  wall  for  each  turn,  but  does  not  reach  it  : 
this  is  the  lamina  spiralis  ossea.  It  extends  through 
all  turns,  and  it  subdivides  tlie  cavity  of  each  turn 
into  an  upper  passage,  or  scala  vestibuli,  and  a  lower, 
or  scala  tympani.  At  the  top  of  the  cochlea  the  two 
seal*  pass  into  one  another  by  the  helicotrema.  The 
scala  vestibuli  opens  into  the  fovea  hemispherica, 
while  the  scala  tympani  at  its  commencement — i.e. 
at  the  proximal  end  of  the  first  turn — would  be  in 
communication,  by  the  fenestra  rotunda,  with  the 
cavum  tympani,  were  it  not  that  this  fenestra  rotunda 
is  closed  by  a  membrane — the  secondary  membrane. 

459.  The  semicircular  canals  start  from,  and  return 
to,  the  fovea  hemi-elliptica  of  the  vestibule. 

The  fenestra  ovalis  leads  from  the  cavum  tympani 
into  the  vestibule — its  hemispheric  division ;  and  this 
fenestra  ovalis  is,  in  the  fresh  condition,  filled  out  by 
a  membrane,  in  which  the  basis  of  the  stapes  is  fixed, 
the  circumference  of  this  being  nearly  as  great  as  that 
of  the  fenestra. 


Internal  Ear.  461 

460.  Tilt'  osseous  labyi-inth  in  all  parts  consists  of 
ordinary  osseous  suUstaiice,  with  the  usual  periosteum 
lining  its  outer  surface  and  its  inner  cavities.  These 
cavities  contain  the  albuminous  fluid  called  perilymph. 
But  they  ;ire  not  tilled  out  by  this,  since,  in  each  of 
the  two  divisions  of  the  vestibule,  in  each  of  the 
semicircular  canals,  and  in  the  cochlea,  is  a  mem- 
branous structure,  analogous  in  shape  to  the  corre- 
sponding division  of  the  labyrinth.  These  membranous 
structures  possess  a  cavity  filled  with  the  same  albu- 
minous fluid  as  above,  called  the  endolymph.  These 
structures  are  disposed  thus  :  in  the  fovea  hemispherica 
is  a  spherical  sac,  called  the  saccule ;  in  the  fovea 
hemi-elliptica  is  an  ellij^tical  sac,  the  lUi^icle  ;  in  each  of 
the  three  semicircular  canals  is  a  membranous  semi- 
circular tube,  which  jiossesses  also  an  ampulla  corre- 
sponding to  the  ampulla  of  the  bony  canal. 

461.  In  the  cochlea  is  a  membranous  canal,  tri- 
angular in  cross-section — the  scala  media  or  cochlear 
duct — -which  also  twists  two  and  a  half  times  from  the 
basis  to  the  apex  of  the  cochlea,  and  is  placed  against 
the  end  of  the  lamina  spiralis  ossea  so  as  to  occupy  a 
position  between  the  peripheral  part  of  the  scala  vesti- 
buli  and  scala  tympani. 

462.  The  different  divisions  of  the  menil)ranous 
labyrinth  are  connected  -  with  one  another  in  this 
manner  :  the  three  semicircular  (membranous)  canals 
open  into  the  utricle  ;  this  does  not  form  a  direct  con- 
tinuity with  the  saccule,  but  a  narrow  canal  comes  off 
both  from  the  saccule  and  utricle  ;  the  two  canals 
join  into  one  minute  membranous  tube  situated  in  the 
aqueductus  vestibuli.  At  its  distal  end  it  enlarges 
into  the  saccus  endolymphaticus,  situated  in  a  cleft  of 
the  dura  mater,  covering  the  posterior  surface  of  the 
petrous  bone.  The  saccule  is  in  communication  with 
the  cochlear  canal,  or  scala  media,  by  a  short  narrow 
tube — the  canalis   reuniens  of    Reichert.      Thus  the 


462  Elements  of  Histology. 

cavity  of  the  whole  membranous  labyrinth  is  in 
direct  communication  throiigliout  all  divisions,  and  it 
represents  the  inner  lymphatic  space  of  the  labyrinth. 
There  is  no  communication  between  the  perilymph 
and  endolymph,  and  the  cavity  of  the  membranous 
labyrinth  stands  in  no  direct  relation  to  the  cavum 
tympani,  since  the  fenestra  ovalis  and  fenestra  rotunda 
both  separate  the  perilymphatic  space,  or  the  cavity 
of  the  bony  labyrinth,  from  the  cavum  tympani.  The 
vibrations  of  the  membrana  tynjpani,  transferred  by 
the  ossicula  auditus  to  the  fenestra  ovalis,  directly 
affect,  therefore,  only  the  perilymph.  The  fluctuations 
of  this  pass  from  the  vestibule,  on  the  one  side, 
towards  and  into  the  perilymph  of  the  semicircular 
canals  ;  and  on  the  other  side,  through  the  scala 
vestibuli,  to  tlie  top  of  the  cochlea,  then  by  the  heli- 
cotrema  into  the  scala  t3^mpani,  and  find  their  conclu- 
sion on  the  membrana  secundaria  closing  the  fenestra 
rotunda.  On  their  way  they  affect  the  membrane  of 
Reissner,  which  separates  the  scala  media  from  the 
scala  vestibuli,  and  also  the  membrana  basilaris  separ- 
ating the  scala  media  from  the  scala  tympani ;  the 
vibrations  of  these  membranes  affect  the  endolymph, 
and  therefore  tlie  nerve-endings  {see  below). 

463.  Sti'U€tiire  of  seiiiicirciilai*  canals, 
utricle  and  saccule. — The  memhranous  semi- 
circular canals  are  fixed  by  stiff  bands  of  fibrous 
tissue  to  the  inner  periosteum  of  the  one  (convex) 
side  of  the  osseous  canal,  so  that  towards  the  concave 
side  there  is  left  the  space  for  the  perilymph.  A 
similar  condition  obtains  with  regaid  to  the  saccule 
and  utricle,  which  are  fixed  by  the  inner  periosteum 
to  one  side  of  the  bony  part. 

The  structure  of  the  wall  is  the  same  in  the  semi- 
circular canals,  utricle  and  saccule.  The  above-men- 
tioned fibrous  ligaments  of  the  periosteum  form  an 
oute7'    coat ;    inside  this    is    a    glassy-looking    tunica 


I.XTEKNAL  Ear. 


463 


propria.  At  one  side  (the  one  away  from  the  bone) 
this  tunica  propria  forms  numerous  papillary  projec- 
tions. The  internal  surface  of  the  membrane  is 
covered  with  a  single  layer  of  polyhedral  epithelial  cells. 

464.  Each  of  the  branches  of  the  nervns  vestibuli 
— i.e.  one  for  the  sac- 
cule, one  for  the  utricle, 
and  three  for  the  three 
ampullae  —  possesses  a 
ganglionic  swelling.  The 
nerve  -  branch,  having 
passed  through  the  mem- 
branous wall,  enters 
special  thickenings  of 
the  tunica  propria,  on 
that  part  of  the  mem- 
branous wall  next  to  the 
bone  :  in  the  saccule  and 
the  utricle  the  thicken- 
ing is  called  macula 
acustica,  in  the  ampullae 
crista  acustica  ( Fig.  -  7  7) 
(M.  8chultze).  This 
thickenin*^  is  a  lar^je 
villous  or  fold-like  pro- 
jection of  the  tunica 
})ropria,  into  which  pass 
the  nerve  fibres  of  the 
several  branches.  These 
tibres  are  all  meduUated  nerve  fibres,  and,  ascending 
towards  the  internal  or  free  surface  of  that  pro- 
jection, form  a  plexus.  In  this  plexus  are  in- 
terspersed numerous  nuclei.  From  the  medullated 
fibres  pass  oS  minute  bundles  or  primitive  fiVjrillse, 
which  enter  the  epithelium  that  covers  the  free 
surface  of  the  projection. 

465.   This    epithelium  is   composejcl  of  a  laver  of 


Fig.  277.— From  a  Transverse  Section 
through  the  Macula  acustica  of  the 
Utricle  of  the  Labyrinth  of  Guiuea- 
pig.     {Atlas.) 

a,  Medullated  nerve  fibres,  forming  plex- 
uses ;  b,  nuclei  of  the  membrane ;  c, 
sensory  epithelium  (diagrammatic);  the 
spindle-shaped  sensory  cells  possess 
long  auditory  hairs  projecting  between 
the  conical  epithelial  cells  beyond  the 
free  surface. 


464 


Elements  of  Histology. 


columnar  or  conical  cells,  between  which  are  wedged 
in  spindle-shaped  cells  ;  V^oth  kinds  possess  an  oval 
nucleus.  According  to  Max  Schultze  and  others,  each 
of  the  spindle-shaped  cells  is  connected  by  its  inner 
process  with  the  nerve  fibrillse  coming  from  under- 
neath :  whereas,  towards  and  beyond  the  free  surface, 


Fig.  278. — Xerve  Terminations  in  the  Epithelium  of  tlie  Macula  acustica. 
The  nerve  fibres  form  denclrons  in  the  epithelial  layer.  (After 
Betzius,  from  Quain.) 


its  outer  process  is  prolonged  into  a  long,  thin,  stiff, 
auditory  hair.  Max  Schultze,  therefore,  calls  the 
columnar  cells  epithelial;  the  spindle-shaped  ones, 
sensory. 

Retzius,  on  the  other  hand,  maintains  that,  in  the 
case  of  fishes  at  any  rate,  the  epithelial  cells  are  those 
which  are  connected  each  with  a  bundle  of  nerve 
fibrillse,  and  that  each  sendi^  <jut  over  the  internal  free 


iNTKRXAr,  Ear.  465 

surface  almiidle  of  iiiie  stiff"  hairs — the  auditory  hairs. 
The  spindle-shaped  cells  of  Max  Schultze,  according 
to  this  theory,  are  only  supporting  cells.  The  free 
surface  of  the  epithelium  is  covered  with  a  homo- 
geneous cuticle,  perforated  l)y  holes  which  correspond 
to  the  epithelial  cells  and  the  auditory  hairs. 

By  Golgi's  method  Retzius  has,  however,  obtained 
evidence  (Fig.  278)  which  shows  that  fine  nerve 
fibres  terminate  by  arborisations  or  dendrons  amongst 
the  epithelial  cells  (Fig    177). 

On  the  internal  surface  of  the  macula  and  crista 
acustica  are  found  the  oUAithx.,  rhombic  crystals,  and 
amorphous  masses,  chiefly  of  carbonate  of  lime,  em- 
bedded in  a  gelatinous  or  granular-looking  basis. 

\^^>.  The  coc'lilca  (Fig.  279),  as  has  been  men- 
tioned above,  consists  also  of  a  bony  shell  and  a 
membranous  canal,  the  former  surrounding  the  latter 
in  the  same  way  as  the  bony  semicircular  canal  does 
the  membranous — i.e.  the  latter  is  fixed  to  the  outer 
or  convex  side  of  the  for-mer.  The  difference  between 
the  cochlea  and  the  semicircular  canals  is  this,  that  in 
the  cochlea  there  is  a  division  of  the  perilymphatic 
space  by  an  osseous  projection — the  lamina  spiralis 
ossea — and  bv  the  scala  media  into  two  scalse,  viz.  the 
(upper)  scala  vestibuli  and  the  (lower)  scala  tympani. 

467.  In  the  osseous  modiolus  are  numerous 
parallel  canals  for  bundles  or  groups  of  the  fibres  of 
the  cochlear  branch  of  the  auditory  nerve  :  these 
canals  open  into  the  porus  internus,  in  which  lies  a 
large  c^ansflion  connected  with  the  nerve. 

Coo 

The  nerve  bundles  are  situated  in  the  canals  of  the 
modiolus,  and  opposite  the  lamina  spiralis  ossea  are 
connected  with  ganglionic  masses — composed  of  bipolar 
ganglion  cells — called  the  ganglion  spirale  of  Corti. 
From  this  ganglionic  mass  the  nerve  fibres  (all  niedul- 
lated)  can  be  traced  into  the  lamina  spiralis  ossea,  in 
which  they  form  rich   plexuses  extending  to  its  outer 

E    E 


Fig.  279.— From  a  Vertical  Section  through  the  Cochlea  of  Ear  of  Guinea- 
pig,  seen  in  the  long  axis  of  the  Modiolus.     (Atlas.) 

a,  Scala  vestibuli ;  b,  scala  tympani ;  c,  srala  media  ;  d,  membrana  tectoria  ;  e, 
cells  of  Claudius ;  /,  upper  outer  angle  of  scala  media ;  g,  region  of  outer 
hair  cells  nn  membrana  basilaris  :  /*,  membrane  of  Reissner;  ?,  epithelium 
linintr  «ulcus  spiralis  (internus)  ;  j,  tunnel  of  Corti's  arch ;  k.  stria  vascularis  ; 
?,  ligamentum  ppirale  :  ?»,  crista  spiralis;  n,  nerve  Hbres  in  lamina  spiralis 
ossea  •  o  gansliun  spirale;  p,  nerve  fibres  in  modit)lus  ;  q.  channels  in  bone 
containing  blood-vessels ;  r,  masses  of  bone  in  modiolus ;  s,  outer  bony 
capsule. 


Internal  Ear.  467 

margin — l.p.  as  far  as  the   membrana  basilaris  of  the 
scala  media  {see  below). 

-4G(S.  From  the  margin  of  the  himina  spiralis  ossea 
to  the  external  bony  shell  extends  the  membrana  basi- 
laris (Fig.  279),  forming  the  lower  and  chief  wall  of 
the  scala  media,  while  the  upper  wall  of  the  canal  is 
formed  by  the  membrane  of  Reissner,  extending 
under  an  acute    an^le  from  near  the    marcrin  of  the 

O  o 

lamina  spiralis  ossea  to  the  outer  bony  shell. 

On  a  transverse  section  through  the  scala  media 
we  see  the  following  structures  : — 

469.  (1)  Its  outer  Avail  is  placed  close  against 
the  periosteum  lining  the  internal  surface  of  the  bony 
shell  ;  it  consists  of  lamellar  fibrous  tissue,  with 
numerous  stitf  elastic  bands,  and  is  the  vestibular 
part  of  a  peculiar  ligament — the  ligamentuTti  spirale 
(Kulliker) — semilunar  in  cross-section,  and  with  its 
middle  angular  })rojection  tixed  to  the  outer  end  of 
the  membrana  basilaris. 

470.  (2)  Its  inner  wall  is  represented  by  an 
exceedingly  delicate  membrane — the  membrane  of 
Reissner :  this  is  also  its  upper  wall,  extending  under 
an  acute  angle  from  the  upper  outer  angle  of  the  scala 
media  to  the  lamina  spiralis  ossea.  But  here  it  is  not 
tixed  on  the  osseous  substance,  but  on  a  peculiar  pro- 
jection on  this  latter — the  crista  spiraUs  (Fig.  279,  m) 
— which  is  a  sort  of  tissue  intermediate  between  tibrous 
and  osseous  tissue,  and  is  added  to  the  vestibular 
surface  of  the  lamina  spiralis  ossea.  This  crista  spiralis 
has  on  one  surface — i.e.  that  directed  towards  the 
scala  media — a  deep  sulcus,  called  the  sulcus  spiralis, 
or  sulcus  spiralis  internus  ;  so  that  of  the  crista 
.spiralis  there  are  two  labia  to  be  distinguished — the 
labium  vestibulare  and  the  labium  tympanicum  ;  the 
former  being  the  upper,  the  latter  the  lower,  boundary 
of  the  sulcus  s})iralis  (Fig.  279). 

471.  (3)    The  lower   wall  of  the    scala   media 


468  Elemexts  of  Histology. 

is  the  memhrana  hasilaris,  extending  in  a  straight 
line  betAveen  the  labium  tynipanicum  of  the  crista 
spiralis  and  the  above-mentioned  projection  of  the 
ligamentum  spirale.  The  scala  media  is  lined  on  its 
whole  internal  surface  with  epithelium,  this  only 
being  derived  from  the  epithelium  forming  the  wall 
of  the  auditory  vesicle  of  the  embryo,  peculiarly 
modified  in  certain  places.  The  scala  tympani  and 
scala  vestibuli  are  likewise  lined  with  a  continuous 
layer  of  flattened  cells — an  endothelium,  which  on 
the  lower  or  tympanic  surface  of  the  mernbrana 
basilaris  is  somewhat  modified,  being  composed  of 
cjranular-lookinof  irre^cnlar  cells. 

472.  As  regards  the  scala  media,  the  epithelium 
lining  its  internal  surface  is  of  the  following  aspect  :— 
Starting  with  the  lower  outer  angle — i.e.  Avhere  the 
mernbrana  basilaris  is  fixed  to  the  ligamentum  spirale 
— we  find  a  single  layer  of  polyhedral  or  short 
columnar  transparent  cells,  lining  this  outer  angle — 
the  cells  of  Claudius ;  ascending  on  the  ligamentum 
spirale,  the  cells  become  shorter,  more  squamous  ;  as 
such  they  are  found  over  a  slight  projection  on  the 
outer  wall — i.e.  the  ligamentum  spirale  accessorium — 
caused  by  a  small  blood-vessel,  the  vas  prominens. 

473.  Then  we  come  to  the  stria  vascularis, 
lining  nearly  the  up[)er  two-thirds  of  the  outer 
wall  of  the  scala  media.  It  consists  of  a  layer  of 
columnar  and  spindle-shaped  epithelial  cells,  between 
which  extend  capillary  blood-vessels  from  the  liga- 
mentum spirale,  and  in  some  animals  (guinea-pig) 
clumps  of  pigment  granules  are  found  between 
them. 

474.  Then  we  pass  from  the  upper  angle  of  the 
scala  on  to  the  membrane  of  Eeissner.  This  consists 
of  a  homogeneous  thin  mernbrana  propria,  covered  on 
its  outer  vestibular  surface  with  a  layer  of  flattened 
endothelium,  and  on  its  inner  surface — i.e.  that  facing 


Internal  Ear.  469 

the  scala  media — with  a  layer  of  less  flattened,  smaller, 
poljdiedral  epithelial  cells. 

475.  We  come  next  to  the  vestibular  labium  of 
the  crista  spiralis,  on  which  are  found  cylindrical 
horizontal  projections  anastomosing  with  one  another  : 
these  are  the  auditor y  teeth  (Huschke).  The  epi- 
thelium of  Reissner's  membrane  is  continued  into  the 
grooves  and  pits  between  the  auditory  teeth  as  small 
polyhedral  cells,  but  over  the  teeth  as  large,  flattened, 
squamous  cells,  which,  passing  on,  line  the  sulcus 
spiralis  and  cover  also  the  tympanic  labium  of  the 
crista  spiralis.  Xow  we  arrive  at  the  membrana 
basilaris,  on  which  the  epithelium  l)ecomes  modified 
into  the  organ  of  Corti. 

476.  The  me  111  bra  11  a  basilaris  consists  of  a 
hyaline  basement  membrane,  on  which  the  organ  of 
Corti  is  fixed  :  underneath  this  is  the  tunica  propria^ 
a  continuation  of  the  tissue  of  the  ligamentum  spirale, 
composed  of  fine  parallel  stiff  fibrils  (Hannover, 
Henle)  stretched  in  a  very  regular  and  beautiful 
manner  in  the  direction  from  the  ligamentum  spirale 
to  the  crista  spiralis  (Nuel).  On  the  tympanic  side 
there  is  also  a  hyaline  basement  membrane.  The 
endothelial  cells  covering  this  on  the  tympanic  surface 
haA'e  been  mentioned  above. 

477.  The  org:aii  of  Corti  (Fig.  280). — Passing 
outwards  from  the  epithelium  lining  the  sulcus  sjiiralis, 
we  meet  with  small  polyhedral  epithelial  cells  in  the 
region  of  the  termination  of  the  lamina  spiralis  ossea, 
next  which  are  columnar-looking  cells — the  inner 
supporting  cells  ;  next  to  these  is  the  inner  hair-cell — 
a  columnar,  or  conical,  epithelial  cell,  with  a  bundle 
of  stitf  hairs,  or  rods,  extending  beyond  the  surface. 
The  inner  hair-cells  form  a  sina^le  file  alonsr  the  whole 
extent  of  the  two  and  a  half  turns  of  the  scala  media. 

478.  Xext  to  the  inner  hair-cell  is  the  inner  rod,  or 
inner  pillar,  of  Corti,  and  next  to  this  the  outer  rod, 


470 


Elements  of  Histology 


or  outer  -pillar,  of  Corti.  Each  forms  a  single  file  for 
the  whole  extent  of  the  two  and  a  half  turns  of  the 
scala  media.  The  two  rods  are  inclined  towards  one 
another,  and  in  contact  with  their  upper  extremity, 


Fig.  2S0.— Organ  of  Corti  of  the  Cochlea  of  Guinea-pig.     (Atlas.) 

a.  Outer  rod  or  pillar  of  Corti :  b,  inner  rod  or  pillar  of  Corti ;  c,  tunnel  of 
arch  of  Corti ;  d,  oucer  hair-cells ;  e,  inner  hair-cell ;  /,  outer  supporting  cells 
containing  fat  globules;  g,  inner  supporting  cells;  /*,  cells  of  Claudius; 
i,  epithelial  cells  lining  the  sulcus  &i>iralis  internus ;  j.  nerve  fibres ;  fc,  part 
of  crista  spiralis. 

or  head :  whereas  the  opposite  extremity,  the  foot, 
rests  under  an  acute  angle  on  the  membrana  basilaris, 
on  which  it  is  firuily  fixed.  The  rest  of  the  rod  is  a 
slender,  more  or  less  cylindrical,  piece — the  body.  The 
outer  rod  is  larger  and  longer  than  the  inner,  the 
latter  being  slightly  bent  in  the  middle.  Owing  to 
the  position  of  the  rods,  the  two  files  form  an  arch — 
the  arch  of  Corti.  Between  it  and  the  corresponding 
part  of  the  basilar  membrane  is  a  space— the  tunnel 
of  the  arch,  triangular  in  cross-section. 

479.  The  substance  of  the  rods,  or  pillars,  of  Corti 
is  bright,  highly  refractive,  and  slightly  and  longitu- 
dinally striated. 

The  head  of  the  inner  rod  is  triangular,  a  short 
process  extending  inwards  towards  the  inner  hair-cell, 
a  long  process  extending  outwards  over  the  head 
of  the  outer  pillar.  Outwards,  the  triangular  head 
possesses  a  concave  surface  grasping  the  convex 
surface   of  tiie  head  of   the   outer   rod.     This  latter 


Internal  Ear.  471 

possesses  a  process  directed  outwards,  which  is  tirnily 
applied  to  the  outer  process  of  the  head  of  the  inner 
rod,  the  two  together  forming  part  of  the  niein))rana 
reticularis  {see  below). 

The  relation  in  size  between  the  outer  and  inner 
rods  is  such  that  the  head  of  one  outer  rod  fits  into 
those  of  about  two  inner  rods. 

480.  At  the  foot,  each  rod  has,  on  the  side 
directed  towards  the  tunnel,  a  granular,  nucleated 
mass  of  protoplasm,  probably  the  remnant  of  the 
epithelial  cell  from  which  the  lower  half  of  the  rod  is 
derived ;  the  upper  part  sometimes  has  a  similar 
nucleated  remnant,  proving  that  this  also  has  been 
formed  b}^  an  ei3ithelial  cell,  so  that  each  rod  is  in 
reality  derived  from  two  epithelial  cells  (Waldeyer). 

481.  Next  follow^  three  or  four  rows  of  outer  hair - 
cells,  similar  in  size  and  structure  to  the  inner  hair- 
cells.  Each  of  the  outer  hair-cells  seen  in  a  section 
belongs  to  a  file  of  hair-cells,  extending  on  the  mem- 
brana  basilaris  along  the  whole  extent — i.e.  two  and 
a  half  turns  —  of  the  scala  media.  Each  hair-cell 
possesses  an  oval  nucleus  and  a  number  of  stifl: 
rods,  or  hairs,  disposed  in  the  shape  of  a  horseshoe  in 
the  outer  jjarb  of  the  free  surface  of  the  cell. 

Four,  and  even  five,  rows  or  files  of  hair-cells 
(Waldeyer),  arranged  in  an  alternating  manner,  are 
found  in  man. 

The  outer  hair-cells  are  also  called  the  cells  of 
Corti  ;  they  are  conical,  and  more  or  less  firmly  con- 
nected with  a  nucleated  spindle-shaped  cell — the  cell 
of  Deiters.  The  two  cells  are  more  or  less  fused  to- 
gether in  their  middle  part  (Nuel).  The  cell  of  Corti 
is  fixed  by  a  branched  process  to  the  membrana 
basilaris,  while  the  cell  of  Deiters  sends  a  process 
towards  the  surface,  where  it  joins  the  memhjrana 
reticularis  {see  below). 

482.  Farther  outwards  from  the  last  row  of  outer 


472 


Elemexts  of  Histology. 


hair-cells  are  columnar  epithelial  cells,  called  the  outer 
supporting  cells  of  Hensen  :  they  form  the  transition 


•s 


5f  •- 


f^  Si 


ss 

S  5 


i  i  §t 


^•3 


^   CO    ... 


Internal  Eak.  473 

to  the  epitlu'lium  lininij  tlie  outer  angle  of  the  scala 
media — i.e.  to  the  cells  of  Claudius. 

In  the  guinea-pig,  the  outer  suppDi-ting  cells 
include  fat  globules. 

483.  The  iii€»<lullat<'d  nerve  fibres,  which  we 
traced  in  a  former  page  to  the  margin  of  the  lamina 
spiralis  ossea,  form  rich  plexuses  in  this,  and  pass 
through  holes  in  it,  in  order  to  reach  the  organ  of 
Corti  on  the  membrana  basilaris.  Looking  from  the 
surface  on  this  part,  we  notice  a  row  of  holes— the 
habenula  perforata  of  Kolliker — a  little  to  the  inside 
of  the  reofion  of  the  inner  hair-cells.  Numerous 
primitive  fibrillse  pass  there  among  small  nucleated 
cells  situated  underneath  the  inner  hair-cells  :  these 
are  the  granular  cells.  Some  of  these  nerve  tibrillse 
— the  inner  bundle  of  spiral  nerve  fibres — become 
connected  with  the  inner  hair-cells;  while  others  — 
the  three  outer  bundles  of  spiral  fibrils  (^Waldeyer) — 
pass,  between  the  inner  rods  of  Corti,  right  through 
the  tunnel ;  and,  further,  penetrating  between  the 
outer  rods  of  Corti,  they  reach  the  outer  hair-cells, 
with  which  they  become  connected  (Gottstein,  Wal- 
deyer).     (Fig.  281.) 

484-.  In  connection  wdth  the  outer  process  of  the 
head  of  the  inner  and  outer  rods  of  Corti,  mentioned 
above,  is  an  elastic  hyaline  membrane — the  lamina 
or  membrana  reticularis.  It  extends  outwards  over 
the  organ  of  Corti  to  the  supporting  cells  of  Hensen, 
and  possesses  holes  for  the  tops  of  the  outer  hair-cells 
and  their  hairs.  The  parts  of  this  membrane  between 
the  heads  of  the  rods  of  Corti  and  between  the  outer 
hair-cells  appear  of  the  shape  of  narrow  phalanges  — 
phalanges  of  Deiters.  A  cuticular  membrane  extends 
from  the  head  of  the  inner  rods  of  Corti  inwards  to 
the  inner  supporting  cells  :  it  possesses  holes  for  the 
tops  of  the  inner  hair-cells. 

485,    From    the    vestibular  labium  of  the  crista 


474  Elements  of  Histology. 

spiralis  to  the  outer  hair  cells  of  the  organ  of  Corti 
extends  a  peculiar  tibrillated  membrane ^the  tnem- 
brana  tectoria.  By  means  of  it  the  sulcus  spiralis 
internus  is  bridged  over,  and  so  converted  into  a 
canal. 

486.  As  we  ascend  towards  the  top  of  the  cochlea, 
all  parts  in  the  scala  media  decrease  gradually  in  size. 
The  organ  of  Corti,  being  of  an  epithelial  nature, 
possesses  no  blood-vessels.  From  the  anatomical 
relations  of  the  organ  of  Corti,  it  appears  most 
probable  that  the  pillars,  or  rods,  of  Corti  act  as  the 
supporting  tissue,  or  framework,  around  which  the 
other  elements  are  grouped :  and  it  seems  likely  that 
the  hair-cells,  with  their  rod-like  hairs  projecting 
freely  into  the  endolymph,  are  the  real  sound-per- 
ceiving elements  of  the  organ  of  Corti.  Their  connec- 
tion with  the  terminal  tilirilhv  of  the  nerves  points  in 
the  same  direction. 

As  indicated  on  p.  460,  all  structures  of  the  scala 
media,  described  in  the  foregoing  pages,  form  an 
uninterru[)ted  succession  through  all  the  turns  of 
the  cochlea. 


I 


475 


CHAPTER  XLIV. 

THE    NASAL    MUCOUS    MEMBRANE. 

487.  The  lower  part  of  the  nasal  cavity  is  lined 
with  a  mucous  membrane  which  has  no  relation  to 
the  olfactory  nerve,  and  therefore  is  not  connected 
with  the  organ  of  smell.  It  is  covered  with  a  strati- 
fied, columnar,  ciliated  epithelium  of  exactly  the  same 
nature  as  that  of  the  respiratory  passages — e.g.  the 
larynx  and  trachea.  Large  numbers  of  mucus-secret- 
ing goblet  cells  are  met  with  in  it.  Below  the  epi- 
thelium is  a  thick  hyaline  basement  membrane,  and 
underneath  this  is  a  mucosa  of  fibrous  tissue,  with 
numerous  lympli  corpuscles  in  it.  In  many  places 
this  infiltration  with  lymph  corpuscles  amounts  to 
diffuse  adenoid  tissue  or  to  perfect  lymph  follicles. 

488.  The  mucosa  contains  in  its  most  superficial 
layer  the  network  of  capillaries,  but  in  the  rest  it 
includes  a  rich  and  conspicuous  plexus  of  venous 
vessels. 

In  the  deeper  parts  of  the  mucous  membrane — 
i.e.  in  the  submucosa — are  embedded  smaller  and 
larger  glands,  the  ducts  of  which  pass  through  the 
mucosa  and  open  on  the  free  surface.  Some  of  the 
glands  are  mucous  ;  others  are  serous.  In  some  cases 
{e.g.  guinea-pig)  almost  all  glands  are  serous,  and  of 
exactly  the  same  nature  as  those  of  the  back  of  the 
tongue.  In  some  places  the  mucous  membrane  is 
much  thicker  than  in  others,  and  then  it  contains 
larger  glands,  and  between  them  bundles  of  non-striped 
muscular  tissue. 


476 


Elements  of  Histology. 


489.  In  the  upper  or  olfartory  i'eg:ioii  (Fig.  282) 
of  the  nasal  cavity  the  mucous  membrane  is  of  a 
different   tint,  Ijeing  more  of   a   brownish  colour;  it 


Fig.  2S-2.— From   a  Section  throiigli  the  Ulfactorj-  Region  of  Guinea-pig. 

{Atlas.) 

a.  Thick  olfactorv  epithelium;  b,  thin  olfactory  epithelium;  c,  ciliated  non- 
olfactorv  einthelium ;  d.  bone.  The  transverse  sections  of  the  olfactory 
nerve  bundles  and  the  tubular  glands  of  Bowman  are  well  seen. 


contains  the  ramifications  of  the  olfactory  nerve,  and 
is  the  seat  of  the  organ  of  smell. 

490.  The  free  surface  is  covered  with  a  columnar 


Nasal  Mucous  Membrane 


All 


cpitlicliuin,   composed  of  tlie  followirg  kinds   of  cells 
(Fig.  283):— 

(«)  A  superficial  layer  of  long  coluniiiar,  or  rather 
conical,  epithelial  cells,  each  with  an  oval  nucleus.     In 


or 


iMjlJ    j    I     IJ    ill   ,1/ 


!i|ipij|i]|i,!,i;jji|,|fir|!i!j||]pi^^^ 


Fig.  283.— From  a  Vertical  Section  tlirongh  the  Olfactory  Mucous  Mem- 
brane of  Guinea-pig.     {Atlas.) 

a,  Epithelial  cells;  ?^,  eensory  or  olfMctory  cells;  c,  deep  epithelial  cells;  d, 
bundles  of  olfactory  uerve  fibres;  e,  the  alveoli  of  serous  (Bowniau's) 
glands. 

some  places  the  free  surface  of  these  cells  is  covered 
with  a  bundle  of  cilia,  similar  to  the  superficial  cells 
of  the  respiratory  j^ai-t  of  the  nasal  cavity  ;  in  most 
places,    however,    the    cilia    are    absent  ;   the    former 


47 


Elements  of  Histology. 


condition  obtains  in  those  places  which  are  in  close 
proximity  to  the  respiratory  region. 

[h)    Between  the  epithelial  cells    extend    spindle- 
shaped  cells,  each  with  a  spherical,  or  very  slightly 


Fig.  284.— From  a  Vertical  Section  through  Olfactory  Membrane  of  Guinea- 
pig.     {Photo.    Moderate  inagnijicat ion.) 

a,  Olfactorv  epithelium ;  b,  mucous  membrane  with  blood-vessel  and  glands  ;  c 
oliactoiy  nerve  fibres  cut  longitudinally. 


oval,  nucleus — the  sensory  cells  (Max  Schultze). 
Each  cell  sends  one  broad  process  towards  the  free 
surface,  over  which  it  projects  in  the  shape  of  a  small 
bundle  of  shorter  or  longer  rods  :  whereas  a  line 
varicose  filament  passes  from  the  cell  body  towards 
the  mucosa,  and,  as  shown  first  by  M.  Schultze,  be- 
comes connected  with  a  fibrilla  of  the  plexus  of  the 
olfactory  nerve  fibres. 


Nasal  Mucous  Membrane. 


A19 


(c)  In  some  places  there  i.s  a  deep  layer  of  epithe- 
Hal  celh^  each  "svitli  a  spliorical  rjiicleus  of  an  inverted 
conical  shape,  their  pointed  extremity  passing  be- 
tween the  other  cells  just  mentioned  and  their  broad 
basis  resting  on  the  basement  membrane  (Fig.  283), 


/' 


\ 


.  '.x^. 


Fig.  285. — Transverse  Section  through  the  Lower  Part  of  the  Nasal  Septum, 
showing  the  (bilateral)  Organ  of  Jacobson  in  cross  section.  {Photo. 
Loic  poicer.) 

1,  Cartilage  extending  above  and  iiartially  around  tlie  organ  ;  -J.  cavity  of 
the  tuljular  organ,  showing  on  its  nit-sial  wall  olfactory  epithelium,  on  its 
lateral  wall  cohnnnar  eiutheliuni ;  3,  cavernous  tissue  in  the  lateral  wall. 


Von  Brunn  has  shown  that  there  is  on  the  free 
surface  of  the  epithelium  a  sort  of  cuticle — a 
delicate  limitans  externa. 

491.  The  mucous  membrane  is  of    loose  texture, 
and  contains  a  rich    plexus  of    bundles  of    olfactory 


4S0  Elements  of  Histology. 

nerve  fibres,  extending  chiefly  in  a  direction  parallel 
to  the  surface  (Fig.  284).  Each  nerve  fibre  is  non- 
meduUated — i.e.  is  an  axis  ( ylinder  composed  of  minute 
or  primitive  til)rilhe.  and  invested  in  a  neurilemma  with 


Fig.  286.— Section  tlirough  the  Front  Part  of  Nasal  Septum  of  Rabbit, 
showing  the  bilateral  organ  of  Jacobson  in  transverse  section.  The 
tube  of  the  organ  of  Jacobson  is  lined  on  its  mesial  wall  with  olfactory 
epithelium.     (Photo.    Loiv  pov:er.) 

g.  Glands  extendiug  from  the  upper  part  of  the  septum  to  the  junction  of  the 
mesial  and  lateral  wall  of  the  organ  of  Jacol'son  ;  c,  rartilage  extending  as  a 
nearly  complete  capsule  around  each  organ  of  Jacobson.  The  lateral  wall  of 
the  organ  contains  cavernous  tissue. 

the  nuclei  of  the  nerve  corpuscles.  Near  the  surface 
tlie  fibres  of  the  plexus  ai-e  thin,  and  they  split  up 
into  the  constituent  fibrils  which  are  directly  con- 
tinuous with  the  fine  varicose  processes  of  the  sensory 
cells  above  named  (Fig.  178). 

492.   The  blood-vessels  supply  with  capillary  net- 


Nasal  Mucous  Mi'Imbrane. 


481 


works  the  superficial  part  of  the  mucous  membrane 
and  the  numerous  glands.  These  are  tlie  (/lands  of 
llownKut,  extending  through  the  thickness  of  the 
mucous  membrane.     They  are  tubes,  slightly  branched, 


Fig.  287.— From  the  same  yeetiou  througli  the  Organ  uf  Jaeobsou  as  in  the 
preceding  figure,  more  magnified.     (Photo.) 

c,  (';irtila,i,'c  of  mesial  wall ;  cf.,  cavernous  tissue  of  lateral  wall.    The  mesial  will 
is  lined  with  thick  olfactory  epithelium. 


and  gradually  enlarging  towards  their  distal  end  ;  in 
some  parts  they  are  more  or  less  straight.  In  struc- 
ture they  are  identical  with  serous  glands,  possessing 
a  minute  lumen,  and  being  lined  with  a  layer  of 
columnar  albuminous  cells.  The  duct  is  a  very  fine 
canal  ;  it  is  that  part  of  the  gland  which  is  situated 
in  the  epithelium  of  the  free  surface ;  it  passes  ver- 
tically through  this,   and  consists  of  a  fine  limiting 

F    F 


482  Elements  of  Histology. 

membrane,  the  continuation  of  the  membrana  propria 
of  the  gland  tube,  and  a  layer  of  very  flattened  epi- 
thelial cells. 

493.  There  is  a  definite  relation  between  the 
size  and  number  of  the  l3undles  of  the  olfactory  nerve 
fibres,  the  thickness  of  the  olfactory  epithelium,  and 
the  length  of  the  gland  tubes.  The  size  and  number 
of  the  bundles  of  the  nerve  fibres  are  determined 
by  the  thickness  of  the  epithelium — i.e.  by  the 
number  of  the  sensory  cells ;  the  number  and  thick- 
ness of  the  olfactory  nerve  bundles  determine  the 
thickness  of  the  mucous  membrane,  and  the  thicker 
this  is,  the  longer  are  the  inlands  of  Bowman. 

494.  The  org-aii  of  Jacobsoii  (Figs,  'l^^'d. 
286,  287)  is  a  minute  tubular  organ  present  in 
all  mammals,  and,  as  has  been  shown  by  Dursy 
and  Kolliker,  also  in  man.  In  mammals  it  is  a 
bilateral  tube,  compressed  from  side  to  side,  and 
situated  in  the  anterior  lower  part  of  the  nasal 
septum.  Each  tube  is  supported  by  a  hyaline 
cartilage,  in  the  shape  of  a  more  or  less  f)lough- 
shaped  capsule — the  cartilage  of  Jacohsoa  —  and 
opens  in  front  directly  into  the  nasal  furrow  (guinea- 
pig,  rabbit,  rat,  etc.);  or  it  leads  into  the  canal 
of  Stenson  (dog),  which  passes  through  the  canalis 
naso-palatinus,  and  opens  immediately  behind  the 
incisor  teeth  on  the  palate.  In  all  instances,  how- 
ever, it  terminates  posteriorly  with  a  bliud  extremity. 

495.  The  cavity  of  the  tube  is  lined  with  stratified 
columnar  epithelium,  which  on  the  lateral  wall  is 
ciliated  in  the  guinea-pig  and  dog,  and  non-ciliated  in 
the  rabbit.  The  median  wall — i.e.  the  one  next  to 
the  middle  line — is  lined  with  olfactory  epithelium 
identical  with  that  of  the  olfactory  region  of  the  nasal 
cavity.  Branches  of  olfactory  nerve  fibres  also  pass 
into  the  median  wall,  and  behave  in  exactly  the  same 
manner  as  in  the  olfactorv  rejjfion.       Numerous  serous 


Nasal  Mucous  Membrane.  483 

glands — belonging    ehietiy  to    the    i^pper    and    hnver 
wall — open  into  the  cavity  of  the  organ  of  Jacobson. 

In  the  lateral  wall  there  is  in  many  instances  a 
plexus  of  veins,  extending  iii  a  longitudinal  direction, 
and  between  the  vessels  are  Imndles  of  non-striped 
muscular  tissue,  thus  constituting  a  sort  of  cavernous 
tissue. 


4«4 


CHAPTER    XLV. 

THE      DUCTLESS      G  L  A  X  D  S. 

496.  I.  The  liypopliy«»i!^  cerebri. — The  upper 
or  smaller  lobe  belongs  to  the  cential  nervous  system. 
The  lower  or  larger  lobe  is  surrounded  by  a  librous 
capsule,  which  sends  numerous  minute  septa  into  the 
interior.  These  split  up  into  numerous  trabeculfe  of 
librous  tissue,  which,  by  di^dding  and  reuniting,  form 
a  dense  plexus,  with  smaller  and  larger,  spherical  or  ob- 
long, or  even  cylindrical  spaces — the  alveoli.  In  these 
lie  spherical  or  oblong  masses  of  epithelial  cells.  These 
epithelial  cells  are  columnar,  j^yramidal,  or  polyhedral, 
each  with  an  oval  or  spherical  nucleus.  Between  the 
epithelial  cells  of  the  same  group  are  found  here  and 
there  small  branched  or  S23indle-shaped  cells,  with  a 
small  flattened  imcleus.  In  some  of  the  groups  or 
alveoli  of  epithelial  cells  is  a  cavity,  a  sort  of  lumen, 
filled  with  a  homogeneous  gelatinous  substance. 

The  interalveolar  connective  tissue  contains  a 
network  of  capillaries.  Between  the  alveoli  and  the 
interalveolar  tissue  there  are  lymph  sinuses,  like  those 
around  the  alveoli  of  other  glands — e.g.  the  salivary 
o-lands. 

497.  II.  The  lliyroid  gland  (Fig.  288).— The 
framework  of  this  gland  is  in  many  respects  similar 
to  that  of  other  glands,  there  being  an  outer  fibrous 
capsule,  thicker  and  thinner  septa,  and  finally  the  fine 
trabecular  forming  the  septa  between  the  gland  alveoli. 
These  are  closed  vesicles  of  a  sjjherical  or  oval  shape, 
and  of  various  sizes.       Each  vesicle  is  lined  with  a 


o 


Due  TL  ESS    Gl  a  XDS. 


4B: 


^  44^#i^^  .^ 


single  layiM-  of  polylicdral  ov  c  »luimi;ir  <'[)itli('lial  cells, 
each  with  a  spherical  or  oval  nucleus.  There  is  a 
cavity,  which  differs  in  size  according  to  the  size  of 
the  vesicle.  It  contains,  and  is  more  or  less  filled 
with,  a  homogeneous,  viscid,  albuminous  fluid — the 
so-called  colloid.  In  this  often  occur  degenerating 
nucleated    lymph  corpuscles  ^ 

and  coloured  Mood  corpuscles 
(Baher). 

498.  The  vesicles  are 
surrounded  by  networks  of 
blood  capillaries.  In  the 
connective-tissue  framework 
lie  networks  of  lymphatics  ; 
between  the  framework  and 
the  surface  of  the  vesicles  are 
lymph  sinuses  lined  with 
endothelium  (Baber).  The 
large  and  small  lymphatics 
are  often  filled  with  the 
same  colloid  material  as  the 
vesicles,  and  it  is  probable 
that  this  colloid  material  is 

and 


%.. 


I 


//   d 


Fi.i,M'8.S. — Fi-Din  a  Section  through 
the  Thyroid  Gland  of  Dog. 

((,  Epitheliiam  lining  the  vesicles; 
h,  coll{  lid  contenr  s  of  the  vesicles; 
c.  lymphatic  tilled  with  the  same 
material  as  the  vesicles  ;  cl, 
tlbrous  tissue  between  the  gland 
vesicles. 


the 


discharged 


carried   away   by 

into  the  circu- 


produced  in  the  vesicles 
lymphatics,  to  be  finally 
lating  blood. 

499.  Its  formation  in  the  vesicles  is  probabh^  due 
to  an  active  secretion  by  the  epithelial  cells  of  the 
vesicles,  and  to  a  mixture  with  it,  or  maceration  by 
it,  of  the  effused  blood  mentioned  above.  In  some 
instances  Bal)er  found  the  amount  of  blood  effused 
into  the  cavity  of  the  vesicles  very  considerable,  and 
hence  it  is  justifiable  to  assume  that  the  destruction  of 
red  blood  corpuscles  forms  one  of  the  functions  of  the 
thyroid  gland. 

"  500.  III.  The  supra-venal  bodies  (Fig.  289). 
— The  supra-renal  body  is  envelojDed  in  a  fibrous  cap- 


486 


Elements  of  Histology 


sule  ;  in  connection  with  this  are  septa  and  trabeculae 

Y-)assing      inwards, 
and    the}^   are    ar- 
ranged   differently 
the  cortex  and 
the 


@  a  .,  ^  t   o  O^^S)  *  •  .'?o-fe-  <^ 


...e 


P'ig.  2S;\  — From  a  Vertical  8eetioii  tlirougli 
The  Supra-renal  Bod}'  of  JVIan.  {Eberth,  in 
Stricl-er's  Manual.) 

1,  Cortical  sulistance  :  2,mP(iullary  part ;  a,  outer 
capsule;  />,  zona  glonierulosa  ;  r.  zona  fascicu- 
lata;  d,  zona  reticularis;  e,  medulla:  /,  large 
vein. 


m 
in 

of    the 
will   be 
sently. 
The 


medulla 
gland,  as 
seen    pre- 

cortex  of 
the  n;land  consists 
of  an  outer,  middle, 
and  inner  zone,  ail 
three  being  di- 
rectly contin  n  o  u  s 
with  one  anothei-. 
The  outer  one  is 
the  zona  rjlomerv- 
losa ;  it  contains 
numerous  sphe- 
rical, or,  more  com- 
monly, elongated, 
masses  of  epithelial 
cells.  The  cells 
are  polyhedral  or 
cylindrical,  each 
with  a  spherical  or 
oval  nucleus.  In 
some  animals — as 
the  dog,  horse — 
the  cells  are  thin 
and  columnar,  and 
arranged  in  a 
t  ran  s  verse  man ner. 
Occasionally  a  sort 
of    lumen    can    be 


discerned  in  some  of  these  cell  masses. 


Ductless  Glands.  487 

501.  Next    follows    the    middle    zone,    or    zona 
fascicvlata.        Tliis    is     the    most     conspicuous     and 

broadest  part  of  the  whole  gland.  It  consists  of 
vertical  columns  of  polygonal  epithelial  cells,  each 
with  a  spherical  nucleus.  The  cell  substance  is  trans- 
parent, and  often  contains  an  oil  globule.  The  columns 
anastomose  with  their  neighbours.  Between  the 
columns  are  tine  septa  of  connective  tissue  carrying 
blood  capillaries. 

Between  the  cell  columns  and  the  connective  septa 
are  seen  here  and  there  lymph  spaces,  into  which  lead 
fine  channels,  grooved  out  between  some  of  the  cells  of 
the  columns. 

502.  Next  follows  the  inner  zone,  or  zona  reticu- 
laris, composed  of  smaller  or  larger  groups  of  poly- 
hedral cells,  with  more  or  less  romided  edges.  These 
cell  groups  anastomose  with  one  another.  The  indi- 
vidual cells  are  slightly  larger,  and  their  substance  is 
less  transparent  than  those  of  the  zona  fasciculata.  In 
the  human  subject  tliey  are  slightly  pigmented. 

503.  In  the  medulla  we  find  cylindrical  streaks 
of  very  transparent  cells  ;  the  streaks  are  separated  by 
vascular  connective  tissue.  The  cells  are  polyhedral, 
columnar,  or  branched.  These  cell  streaks  anasto- 
mose with  one  another  and  are  directly  continuous 
with  the  cell  groups  of  the  zona  reticularis  of  the 
cortex. 

504.  The  cortex  is  richly  supplied  with  dense 
networks  of  caj)illary  blood-vessels ;  their  meshes  are 
polyhedral  in  the  outer  and  inner  zone,  elongated  in 
the  middle  zone,  or  zona  fasciculata.  In  the  medulla 
numerous  plexuses  of  veins  are  met  with.  In  the 
centre  of  the  supra-renal  body  lie  the  large  efferent 
venous  trunks.  In  the  capsule  (Kolliker,  Arnold), 
and  in  the  connective  tissue  around  the  central  veins, 
are  plexuses  of  lymphatic  tubes  with  valves.  The 
nerves    are    very    numerous    and    composed    of    non- 


/ 


4SS  Elemexts  of  Histology. 

medullated  fibres ;  in  the  medulla  they  form  rich 
plexuses.  In  connection  with  these  and  with  those  of 
the  outer  capsule  are  smill  ganglia  (Holm,  El)9rth). 

505.  IV.    The     g^laiidiila     coccygea     and 

iiiter-rarotic-a. — The  lirst  of  these  is  a  minute 
corpuscle  situated  in  front  of  the  apex  of  the  os 
coccygis,  and  was  discovered  by  Luschka.  The 
glandula  carotica  of  Luschka  (ganglion  inter-caro- 
ticum)  is  of  exactly  the  same  structure  as  the 
glandula  coccygea. 

506.  Its  framework  is  of  about  the  same  nature 
as  that  of  other  glands — a  fibrous  capsule  and  inner 
fibrous  septa  and  trabecular.  The  septa  and  trabeculae 
contain  in  some  placs-s  bundles  of  non  striped  muscular 
tissue  (Sertoli). 

507.  The  spaces  of  the  framework  are  occupied  by 
the  parenchyma.  This  consists  of  spherical  or  cylin- 
drical masses  of  cells  connected  into  networks.  The 
individual  cells  are  polyhedral  epithelial  cells,  each 
with  a  spherical  nucleus.  According  to  Luschka,  in 
the  newly-born  child  they  are  ciliated.  In  the  centre 
of  each  of  the  cell  masses  lies  a  capillary  blood-v^essel, 
much  convoluted  and  wavy. 

Numerous  non-medullated  nerve  fibres  forming  a 
plexus  are  situated  in  the  framework  of  the  gland. 


I  X  D  E  X 


Alxlneens,  222 
Absorption  {see  Lymphatics) 
Accessory  nucleus,  210 
Achruiiiatin,  11 
Acini  of  glands,  292 

of  liver,  333 

of  pancreas,  330 

Acoustic  ganglion,  219 
Adenoid  reticulum,  62,  126 

tissue,  126 

A' 1  maxillary  glands,  289 
Adveutitia  of  arteries,  108 

of  capillaries.  111 

of  veins,  110 

lymphatic  vessels,  118 

Agminated  glands,  130 
Air  cells,  345 
Alje  nasi,  63 
Albuginea  of  ovary,  3S7 

of  testis,  372 

Albumin  membrane  of  Ascherson, 

402 
Albuminous  cells,  293 
Alloplasmatic  organs,  6 
Alveolar  ca\'ity,  275 

ducts,  345 

Alveoli  of  glands,  292 

of  lung,  345 

of  pancreas,  330 

Alveus,  249 
Amacrines,  450 
Amitotic  division,  12 
Amwboid  corpuscles,  4 

■  movement,  4,  5,  24,  58 

Amphophile  cells,  27 

Ampulla,  460 

Anterior  column  of  cord,  17<'> 

corpus  quadrigeminura,  231 

grey  commissure.  174 

horn  of  cord,  173 

lateral  tract,  179 

nerve-roots  from  cord,  187 

white  commissure,  187 

Aorta,  109 
Aponeurosis,  47 
* 


of    spinal 


Aqueduct  us  Sylvii,  220 

vestibuli,  461 

Arachnoid     membrane 

cord,  170 

of  brain,  235 

Arachnoidal  villi,  235 

Arborisation,  151 

Arenate  fibres  of  medulla,  213 

Areolar  tissue,  48 

Arrector  pili,  419 

Arteriaj  ciliares  breves,  440 

recurrentes,  440 

helicinte,  385 

rectse,  369 

Arteries,  108 
Arterioles,  Afferent,  55 

of  uterus,  397 

Articular  cartilage,  63,  82 

nerve-corpuscles,  161 

Arjiienoid  cartilage,  339 
Ascending  degeneration,  180 

loop-tube,  364 

root  of  glosso-pharyngeal  nerve, 

210 

of  the  eighth  nerve,  215 

of  the  fifth  nerve,  224 

Aster  stage  in  nucleus,  15 
Attraction  sphere,  9 
Auditory  hairs,  464 

nen'e.  Origin  of,  217 

,  Division  of,  219 

teeth,  469 

Auerbaoh's  plexus,  326 

Auricle  of  heart,  107 

Aiiriculo-ventricular  valves,  106 

AxUemma,  145 

Axis  cylinder,  144 

process    of   sympathetic 

ganglion  cell,  263 
Axon,  144 


Bartholin's  glands,  399 
Basement  membranes  of  skin,  405 


490 


Elements  of  Histology. 


Basilar  membrane  of  cochlea,  46ft 

Basket  cells  of  cerebellum,  241 

Basophile  cells,  27 

Bellini's  ducts,  305 

Bile-duets,  330 

Bile  capillaries,  336 

Bilirubin,  23 

Bioblasts,  9 

Bladder,  S7,  371 

Blastoderm  of  chick,  2 

Blood,  19 

corpuscles,  19 

,  their  origin,  2S 

cysts,  115 

islets,  115 

glands  of  His,  126 

platelets  of  Bizzozero,  27 

-vessels,  105 

Bone,  6S 

cartilage,  6S 

cells,  71 

corpuscles,  71 

,  Development  of,  74 

trabecultf ,  74 

Bowman's  capsule,  360 

elastica  anterior,  42!' 

glands,  481 

membrane,  429 

sarcous  elements,  94 

Brachia,  233 

Brain  membranes,  235 

structure,  243 

Bronchi,  343 

BrowTiian     molecular    movement. 

300 
Bruch,  Glands  of,  427 
Briicke's  elementary  organisms,  5 

oikoid  and  zooid,  22 

tunica  nervea,  456 

Brunner's  glands,  328 
Buccal  glands,  298 
Bulbus  olfactorius,  250 
Biitsclili's  nuclear  spindle,  15 


Calcification  of  bone,  So 

of  cartilage,  65 

• of  dentine,  283 

Calices  of  kidney,  356 
Canal  of  Schlemm,  434 

of  Stenson,  482 

of  Stilling,  444 

Canalis  hyaloideus,  322,  444 

Petiti,  443 

reuniens,  461 

Canaliculi  in  bone,  70 

in  cartilage,  65 

Capillaries  of  marrow-bone,  111 


Capillaries  of  nerve  system,  111 
Capillary  bile-ducts,  336 

blood-vessels.  111 

•  lymphatics,  119 

network  in  mucosa,  801 

sheaths,  354 

Capsule  of  Bowman,  360 

of  ganglion  cells,  255 

of  Glisson,  333 

of  kidney,  356 

of  the  spleen,  351 

Cartilage,  63 

,  Articular,  64 

capsule,  64 

cells,  63 

,  Elastic,  67 

,  Fibrous,  66 

,  Hyaline,  63 

,  Lacun*,  63 

of  Jacobson,  482 

of  Luschka,  339 

Cavernous  tissue  in  tactile   liairs, 
418 

in  organ  of  Jacobson.  483 

tissues  in  genital  oigans,  384 

Cavities  of  tendon  sheaths,  121 
Cavum  tympani,  459 
Cell  enclosures,  9 

protoplasm,  7 

Cells,  5 

,  Muscular,  of  blood-vessels,  88 

,  of  intestine,  88 

,  of  respiratory  organs,  88 

-,  of  stomach,  88 

,  of  urinary  organs,  88 

in  tadpole's  tail,  50 

of  Claudius,  468 

of  Corti,  471 

of  Deiters,  236.  471 

of  Golgi,  242 

of  Martinotti,  246 

of  Purkinje,  239 

Cellulai  mastoide*,  4.59 
Cellular  tissue,  48 
Cement  of  teeth,  279 

substance,  30 

of  endothelium,  40 

of  epithelium,  30 

of  fibrous  tissue,  47 

Central  canal,  185 

grey  nucleus,  185 

Centroacinous  cells,  331 
Centrosome,  9 
Cerebellum,  237 
Cerebrum,  243 
Ceruminous  glands,  409 
Cer\ix  of  uterus,  395 
Chalice  cells,  36 
Chondrin,  46,  63 


l.VDEX. 


491 


Chondroclasts,  S:'> 

Choroidal  portion  of  ciliary  muscle, 

87 
Choroid  lueinbrane,  440 
Chromatic    granules    in     ganglion 

cells,  1H4 
Chromatin,  11 
Chromosomes,  11 
Chyle,  S-M 

vessels,  31i> 

Ciliary  muscle,  435 

nerves,  43S 

processes,  438 

Cilia,  404 
Ciliated  eells,  3o 
Circulus  arteriosus  in  iris,  438 
Circumanal  glands,  409 
Circumcellular  plexus,  265 
Cisterna  lymphatica  magna,  1-21 
Clarke's  columns,  H»2 
Cleavage  of  ovum,  2 

of  white  blood  corpuscles,  25 

Clitoris,  309 

Cochlea,  465 

Cohnheim's  areas,  93 

Colloid,  4S5 

Colostrum  corpuscles,  403 

Coloiu-ed  blood  corpuscles,  19 

Colourless  blood  corpuscles,  23 

Columnar  epithelial  cells,  30 

Commatract,  179 

Commissure,  Grev,  of  spinal  cord, 

173 

,  Wliite,  of  spinal  cord,  187 

Compound  lymphatic  glands,  134 
Concentric  bodies  of  Hassall,  132 

lamellie,  72 

Cone  fibre,  451 
Cones  of  retina,  452 
Coni  vasculosi,  379 
Conjunctiva,  424 

blood-vessels,  426 

bulbi,  426 

lymphatics,  427 

nerves,  427 

palpebrse,  424 

Connective  tissue,  46 
Contractility  of  corneal  corpuscles, 

52 

of  pigment  cells,  54 

Contraction  of  muscle,  99 

wave,  99 

Convolution  of  brain,  243 

in  nucleus,  13 

Corda?  tendinete,  106 
Cords  of  adenoid  tissue,  127 
Coriuni,  404 
Cornea,  50,  429 
nerves  in,  431 


Corneal  cells,  50 

corpuscles,  50,  430 

Cornuain  cord,  173 
Cornua  uteri,  396 
Corpora  cavernosa,  384 

geniculata,  270 

quadrigemina,  226 

striata,  249 

Corpus  callosum,  249 

Highmori,  372 

luteum,  391 

restiforme,  209 

spongiosum,  384 

Corpuscles,  Malpighian,  353,  359 

of  blood,  20,  23 

of  bone,  71 

of  connective  tissue,  48 

of  Grandry,  160 

of  Herbst,  158 

of  lymph,  123 

of  Meissner,  158 

of  muscle,  94 

of  nerve,  145 

■ of  Pacini,  155,  423 

of  Vater,  155 

,  Tactile,  158,  423 

Corti's  arch,  470 

cells,  471 

ganglion,  465 

organ,  469 

rods,  469 

Cortical  layer  of  ovary,  387 

lymph-sinus,  136 

Costal  cartilages,  63 

pleui-a,  122 

Cowper's  glands,  383 
Cremaster  internus,  381 
Crenate  blood  corpuscles,  21 
Crescents  of  Gianuzzi,  294 
Cricoid  cartilage,  339 
Crista  acustica,  338 

spiralis,  342,  347 

Crus  cerebri,  229 

,  Crusta  of,  233 

Crusta  petrosa,  463 
Crypts,  129 

of  Lieberklihn,  318 

Cuticle  of  Xasmyth,  284 
Cutis  anserina,  420 

■ vera,  404 

Cystic  duct,  SS 
Cytogenous  tissue,  126 
Cytoplasm,  7 


Deiters'  cells,  236,  471 

phalanges,  473 

Demilunes  of  Heideuhain, 


294 


492 


Elements  of  Histology, 


Dendrite,  197 
Dendron,  151 
Dentinal  canals,  277 

fibres,  277 

sheaths,  277 

tubes,  85 

Dentine,  So 

Descemet's  membrane,  ijl,  430 

Diapedesis.  113 

Diaphragm,  44, 122 

Diaster  stage  in  nucleus,  16 

Diffuse  adenoid  tissue,  127 

Dilatator  puiiiUte,  437 

Direct  division,  12 

"Disetactil,"  161 

Discus  p>roligerus,  390 

Disdiaclasts,  104 

Dispireme,  IG 

Distal  convoluted  tubes,  365 

Division,  Remak's  mode  of,  12 

Doyere's  nerve-mount,  165 

Ductless  glands,  484 

Ducts  of  pancreatic  gland,  330 

of  salivary  gland,  291 

Ductus  ejaculatorii,  381 
Dui-a  mater,  170 
Dural  sheath,  457 


Ear,  External,  458 

,  Internal,  460 

Ectoplasm,  8 
Eosinophile  cells,  27 
Efferent  lymphatics,  138 

medullated  nerve-fibres,  ISS 

veins,  56 

Elastic    fenestrated    membrane    of 

Henle,  61 
Elastin,  60 
Electric  nerve,  14S 
Eleidin,  33 
Elementary  fibrill*,  145 

fibrils,  47 

organisms,  5 

Enamel,  275 

cap,  281 

cells,  281 

organ,  280 

•  prisms,  275 

End-bulbs  of  Krause.  159 

Endocardium,  105 

Endochondral  formatio     of  bone, 

75 
EndoljTQph,  461 
Endolympliangial  nodules,  128 
Endomysium,  91 
Endoneurium,  142 
Endoplasm,  8 


Endothelial  cells,  structure,  40 

membrane,  40 

Endothelium,  40 

Endotheloid  ceU-plates,  126 

Energid,  6 

Engelmann's     intermediate      disc, 

95 
Ependvma,  211 
Epidermis,  33,  404 
Epididvmis,  379 
Epiglottis,  67,  339 
Epineurium.  i41 
Epithelial  cells,  30 

,  Division  of,  38 

,  Regeneration  of.  38 

Epithelium,  30 
Ergastic  structures,  6 
Erythi-oblasts,  28 
Eustachian  tube,  459 
External  arcuate  fibres,  213 
Eyeball,  426 

lashes.  424 

lids,  424 


Fascise,  48,  49 
Fascia  dentata,  249 
Fascicles,  91 
Fasciculus  cuneatus,  178 

of  Goll,  179 

of  Lissauer,  179 

pjrramidal,  177 

Fat  cells,  55 

and  starvation,  58 

Fenestra  ovalis,  460 

rotunda,  460 

Fenestrated  membrane,  45,  48 

of  Henle,  61 

Fertilisation  of  ovum,  2 

Fibrfe  arcuat«,  213 

Fibres.  Connective  tissue,  46 

,  Elastic  tissue,  60 

of  muscle,  86,  91 

of  nerves,  140 

of  Puikinje,  106 

Fibrillie  of  connective  tissue,  47 

of  muscle,  92 

of  nerve,  145 

Fibro-cartilage,  Q() 

Fibrous  tissue  development,  59 

Fillet,  225 

Fissura  orbitalis,  88 

Fissure  of  Rolando,  243 

Fissures  of  spinal  cord,  175 

of  medulla,  202 

Foetal  tooth  papilla,  280 
Follicles,  Hair,  409 
,  Lieberklihn's,  318 


Index. 


493 


Follicles,  Lyinpb,  12ti 

,  8ebac»'oiis,  418 

,  Thyiuus,  131 

Fornix  conjunctivae,  426 

vatdna?,  3'.»S 

Fossa  glenoidalis,  66 

navicularis,  383 

IKJtcllari.s,  443 

Fovea  centralis,  455 

hemielliptica,  460 

hemispherica,  460 

Fuhilus  of  peptic  gland,  312 
Funiculus  cuneatus,  202 
gracilis,  202 


Gall-bladder,  336 

Ganglia,  Cerebro-spinal,  253 

,  Svmpathetic,  25tt 

Ganglion  ceUs,  191,  239,  243,  253 
Gasserian  ganglion,  253 
Gelatinous  tissue,  62 
Geniculate  ganglion,  270 
Genital  coq>uscles  of  Krause,  160 

end-corpuscles,  1 55 

organs  (male),  372 

(female),  386 

Germ  reticulum  of  von  Ebner,  377 
Germinating  cells,  44 

endothelial  cells,  43 

epithelium,  387 

spots,  1,  388 

vesicle,  1,  388 

Giralde's  organ,  380 
Gland,  Prostate,  382 
Glunds.  agminated,  130,  321 

,  Bartholini,  399 

,  Bionchial,  349 

,  Brunner,  328 

,  Buccal,  298 

,  Carotic,  488 

,  Ceruminous,  409 

,  Coccygeal,  4SS 

,  Harder,  428 

,  Krause,  426 

,  Laclirymal,  427 

-.  Lieberkiihn's,  318 

.  Littre's,  383 

,  Lymphatic,  126,  134 

.  Meibomian,  424 

.  Mohl,  425 

,  ilucous,  287,  -298 

.  Peptic.  312 

.  Pever,  321 

,  Pyloric,  313 

,  Salivary,  286 

,  Sebaceous,  418 

,  Serous,  286,  299 


Glands,  Solitary,  130 

,  Submaxillary,  286 

-: ,  Sweat,  407 

,  Thynuis,  131 

,  Thyroid,  484 

Glandulie  agminat^e,  ISO 

lenticulares,  315 

Pacchioni,  235 

uteri  nte,  396 

Glans  clitoridis,  399 

penis,  384 

Glassy  membrane,  411 
Glissons  capsule.  .333 
Globulin,  21 
Globus  major,  380 
Glomeruli.  251,  360 
Glycogen,  9,  23,  335 
Goblet  cells.  36 
Golgi's  eeUs,  242 

method,  182 

tendon  spindles,  167 

Goll's  tract,  179 
Graafian  follicles,  388 
Grandry's  corpuscles,  160 
Granular  leucocytes,  26,  58 
Granules  in  blood,  27 
Granulosa,  membrana,  388 
Grey  commissure,  174 
Ground  lamelhe,  73 

plexus  of  Arnold,  162 

substance,  46 

Growing  capillaries,  113 


Habenula  X'erforata,  473 
Hajmatin,  23 
Haematoidiu,  23 
Hsematoplasts,  27 
Hiemin  crystals,  23 
H*nioglobin,  22 

cnstals,  23 

Hah-,  414 

bulb,  412 

,  Development  of,  416 

fibres,  413 

foUicles,  409 

knob,  416 

,  Marrow^  of,  413 

,  Xew  formation  of,  415 

l>apilla.  411 

,  Root  of.  413 

sheath  of,  412 

sac.  411 

,  Shaft  of,  414 

Harder's  gland,  428 
Haversian  canals,  72 

lamellie,  72 

spaces,  74 


494 


Elements  of  Histology. 


Heart  anrl  blond-vessels,  105 

Helicotrenia,  469 

Henle.  Fenestrated  membranes  of, 

•51.  lOS 

,  Fibres  of,  62 

,  Sheath  of,  142 

.  Stratum  nervemii  of,  456 

,  Tulies  of,  364| 

Hensen's  cells,  472 

median  disc,  9S 

Hepatic  cells,  335 

duct,  336 

lobules,  333 

veins,  335 

Herbst,  Corpuscles  of,  158 
Hilum  of  lymph  glands,  134 

of  salivarj-  glands,  291 

of  spleen,  352 

Hippocampus,  249 

Homogeneous   elastic   membranes, 

61 
Howship's  lacunse,  85 
Huxley's  layer,  414 
Hyaline  cartilage,  ii3 

leucocyte,  26 

Hyaloid  membrane,  443 
Hyaloplasm,  7 
Hypophysis,  484 


Ileum,  321 

Incremental  lines  of  Salter,  278 

Incus,  459 

Indirect  division,  13 

Infundibula,  88 

of  bronchiole,  345 

of  gland,  299 

Inner  molecular  layer,  449 

nuclear  layer,  449 

Interarticular  cartilages,  66 
Interfascicular  spaces,  49 
Interglobular  spaces    of  Czermnk. 

278 
Interlobar  ducts,  291 
Interlobular  bile-ducts,  336 

connective  tissue  of  liver,  333 

ducts,  291 

Intennediate  cartilage,  66 

disc,  96 

plexus,  162 

zone,  315 

Intermembranous      formation      of 

bone,  S3 
Intermuscular  fibrils,  163 
Internal  arcuate  fibres,  213 

cajjsule  of  brain,  233 

Intervertebral  discs,  66 
Intestine,  Large,  317 


Intestine,  Small,  317 
Iiitima  of  arteries,  108 
Intralobular  bile-capillaries,  336 

veins,  335 

Intranuclear  network,  11 
Iiis,  436 

.  Blood-vessels  of,  438 

;  Lymph-clefts  of,  438 

,  Lymph-sinuses  of,  438 

,  Nerve-fibres  of,  438 


Jacobson's  organ,  482 


Karyokinesis,  13 
Karyomitosis,  13 
Karyoplasm,  11 
Keratin,  33 
Kidney,  356 

,  Afferent  arterioles  of,  368 

blood-vessels,  367 

glomerulus,  360 

lymphatics,  370 

parenchyma,  357 

vessels,  367 

Killliker's  muscle  buds,  102,  166 

muscle  spindle,  102 

osteoclasts,  85 

tract  cells,  197 

Kilhne's    nerve-ending    in  muscle, 
164 

rhabdia,  92 

rhodopsin,  453 

sarcoglia,  100 


Labia  pudendi  majora,  420 
Labium  tymjianicum,  467 

vestibulare,  467 

Labyrinth,  Osseous,  460 
Lachrj'mal  glands,  427 
Lacunfe  Morgagni,  383 

of  bone,  70 

of  cartilage,  63 

— —  of  lymphatics,  51 
Lamellai  of  bone,  70 

of  cornea,  429 

of  lens,  442 

Lamina  cribrosa,  456 

elastica  of  cornea,  429 

fusca,  434 

reticularis,  473 

spiralis  ossea,  460 

vitrea,  438 

Langerhans'  gi'anular  layer,  34 


Index. 


495 


Larvnx,  330       r 
Lateral  fillet,  228 

horn,  174 

nucleus,  211 

tract,  175 

Lemniscus,  214 
Lens.  442 

tibres,  442 

stars,  443 

Lenticular  plands,  l.iO 
Lencajmia,  20 
Leucocyte,  23 
Leucocj-tosis,  20 
Leucopenia,  20 
Ligamentuni  denticulatum,  171 

latum,  386 

pectinatum,  434 

pulmonis,  347 

spirale,  4(57 

suspensory  of  lens,  443 

Liniitans,  externa,  451 

interna,  447 

Lines  of  Salter,  278 

of  Schreger,  279 

Liquor  folliculi,  390 

sanguinis,  19 

Littre's  glands,  388 
Liver,  333 

,  Vessels  of,  335 

Lobes  of  pancreas,  330 

of  salivary  gland,  200 

of  thymus  gland,  131 

of  lung,  346 

Lobules  of  liver,  333 

of  lung,  346 

of  salivary  glands.  290 

of  thymus  gland,  131 

Locus  ccenileus,  228 
Lung,  346 

blood-vessels,  349 

Ivmphatics,  349 

Lymph,  123 

Lvmphatic  capillaries.  119 

^—  clefts,  119 

glands,  126,  134 

rootlets,  119 

sinuses,  120 

tissue,  62,  126 

vessels,  117 

Lymphatics,  117 

in  mucosa,  302 

Lymph-canal  system  in  cornea,  51 

-canalicular  system,  119 

cavities.  120 

corpuscles,  123 

follicles,  126 

hearts,  123 

Lymphocyte,  25,  58,  123 
Lymiihoid  cells,  25 


Macula  acustica,  463 

lutea,  454 

Malleus,  459 

Malpighian  corpuscles  of   kidney, 
359 

of  spleen,  353 

pyramids  of  kidney,  357 

stratum  of  skin,  33 

Mammary  gland,  401 
Manubrium  mallei,  459 
Marchi's  method,  182 
Marrow  of  bone,  68 
Matrix  of  osseous  substance,  70 
^Meatus  auditorius  extemus,  458 
Meckel's  ganglion,  253 
Media  of  arteries,  108 
Median  fillet,  228 

lateral  fissure,  176 

^fediastinum  testis,  372 
Medulla  oblongata,  202 

of  gland, 134 

Medullary  cylinders,  135 

lymph-sinus,  136 

ray,  359 

sheath  of  nerve-fibres,  145 

Medullated  nerve-fibres,  143 
Meibomian  glands,  424 
Meissner's  corpuscles,  158,  423 

plexus,  261,  266,  326 

Membrana  basilaris,  469 

•  chorio  capillaris,  441 

Descemeti,  430 

granulosa,  388 

hyaloidea,  443 

reticularis,  473 

secundaria,  460 

supra-choroidea,  434 

tectoria,  474 

tympani,  458 

Membrane  of  Krause,  96 
Mesencephalon,  229 
Mesentery,  122 
Mesogastrium,  45 
Metakinesis,  15 
Microcytes,  20 
Microsomes,  9 
Migratory  cells.  44 
Milk,  403 

•  globules.  402 

tooth,  283 

Mitoina,  11 
Mitral  cells,  251 
Modiolus,  465 
Monaster,  15 
Motor  ganglion  cells,  197 
Moss  fibres,  243 
Movement  of  cilia,  35 
Mucin,  37 
Mucosa,  300 


496 


Elements  of  Histology. 


Mucosa,  Lymph  follicles  of,  128 
Mucous  cells,  2'.)3 

glands,  2Sr,  298 

membrane,  300 

Miico-salivary  glands,  288 
Mucus,  Formation  of,  36 
Miiller's  fibres,  447 

muscle,  435 

Muscle  bundles,  87,  !)1 
— —  buds,  102 

cells,  86 

column,  92 

corpuscles,  94 

libres,  86,  90 

librillEe,  92 

sheath,  87 

spindle,  102 

tissue,  Striped,  90 

.  Non-striped,  86 

Muscular  compartments,  98 
Muscularis  externa,  308 

mucosEe,  308 

Musculus  ciliaris  Riolani,  424 
Myeloplax,  7,  85 
Myeloplaxes  of  Robin,  85 


Xail,  420 

cells,  420 

groove  420 

substance,  420 

Xasal  mucous  membrane,  475 

sei)tum,  63 

Nerve  bundles,  141 

corpuscles,  145 

end  plate,  16o 

endings,  155 

fibres,  140 

plexus,  143,  150 

unit,  268 

Network  of  fibrill*,  153,  167 
Neurilemma,  145 
Neuroglia,  182 

cells,  184 

fibrils,  183 

of  Virchow,  182 

•  tissue,  62 

Neuraxon,  144 

Neuron,  268 

Neurokeratin,  146 

Neutropliile  cells,  27 

Nipple,  401 

Non-medullated  nerve-fibres,  148 

Nuclear    layer    in     bulbus    olfae- 

torius,  251 
membrane,  11 

substance,  11 

zone,  442 


Nucleoli,  11 
Nucleoplasm,  11 
Nucleus,  .Structure  of,  H 
Nucleus  ambiguus,  215 

arciformis,  213 

cuneatus,  206 

gracilis.  206 

Nuclei,  Inner,  of  retina,  449 

,  Outer,  of  retina,  451 

Nymphae,  399 


Odontoblasts,  277,  280 
0']sophagus,  307 
Olfactory  bulb,  250 

cells,  478 

glomeruli,  251 

nerves,  148,  480 

Olivary  bodies,  206,  207 

nucleus,  207 

Omentum  of  cat,  44 

of  frog,  122 

of  guinea-pig,  45 

of  rat,  45 

,  Structure  of,  48 

Optic  chiasma,  270 

lobes,  231 

nerve,  456 

nerve-fibres,  447 

tract,  270 

■  vesicle,  455 

Ora  serrata,  447 
Organ  of  Corti,  469 

of  Giralde,  380 

of  Jacobson,  482 

Ossein,  70 

Osseous  labyrinth  of  ear,  460 

lamella;,  70 

substance  from  osteoblasts,  85 

Ossicula  auditus,  459 

Ossifying  cartilage,  77 
Osteoblasts  forming  bone,  84 
Osteoclasts,  85 
Osteogenetic  layer,  68 
Otoliths,  339 
Oval  nucleus,  41 
Ovary,  386 

,  Development  of,  392 

,  Lymphatics  of,  282 

,  Nerves  (jf,  282 

Oviduct,  394 
Ovum,  1,  388 
Oxyntic  cells,  312 
Oxj-phile  cells,  27 


Pacinian  corpuscles,  155 
Palate,  298 


Index. 


497 


Palmiii  plicata\  305 
Pallicbni',  4-24 
Pancreas,  330 
Papilla  oircimivallata,  305 

liliJormis,  30-' 

foliata,  .•i05 

fmi^iformis,  302 

iiervi  optiri,  44t) 

Papillary  hair  ofUiiiia,  410 

muscle,  ItiC. 

Paraglobiilin,  22 
Paraiiuck'i,  IS 
Paraplasm,  51 
Parenchyma  of  kidney,  357 
Parenchymatous  cartilage,  66 
Parietal  cells,  312 

Pars  ciliaris  retiuic,  430 

niembranacea,  3S3 

prostatica,  383 

Pedunculated     hydatid     of     .Alor- 

gagni,  380 
Pedunculus  cerebelli,  238 
Penis,  384 

corpora  caveinosa,  3S4 

nerve-endings,  IGO 

Peptic  glands,  312 
Peribronchial  lymphatics,  340 
Pericardial  cavity,  121 
Pericellular  space,  201 
Pcrichimdriuni,  ti3 
Perilymph,  401 
Perilynjphangial  nodules,  128 
Perimysium,  01 
Perineurium,  141 
Periosteal  bone,  75 

f(jrmation,  84 

j)tocesses  of  Virchow,  75 

Periosteum,  68 

Peripheral  nerve-endings,  155 
Peritoneal  cavity,  121 
Peritoneum,  41 
Perivascular  lymphatics,  110 

lymph  spaces,  201 

Peyer's  ulands,  321 

-  -  pat'rh,  130 
Phagocvtes,  25,  50 
Pharynx,  208 

tonsil,  302 

Pia  mater,  170,  235 
Pial  sheath,  456 
Pigment  cells,  52 
Plasma,  10 

cells,  50 

Pleura  pulmonalis,  347 
Pleural  cavities,  121 
Plexus  choroideus,  235 

myentericus,  326 

Meissner,  326 

venosus  vaginalis,  308 


Plica}  villosa?,  311 
Polar  bodies,  18 
Pons  Varolii,  226 
Porta,  hepatis,  333 
Portio  iMiilleri,  435 

vaginalis  uteri,  305 

Posterior  nerve  roots  from  spinal 

cord,  188 
Postganglionic  libres,  2r)4 
Pricganglionic  fibres,  265 
Prickle  cells,  37 
Primitive  dental  groove,  280 

tibrilhe,  15U 

fibrils,  02 

ova,  393 

Prostate,  382 
Protoblast,  6 
Protoplasm,  1,  7 

,  ^5tructure  of,  7 

Protoplasmic  memlirane,  55 
Proximal  convoluted  tubule,  362 
Pulp  tissue,  270 

Purkinje's  ganglion  cells,  239 
Pyloric  glands,  313 
Pyramid  of  Ferrein,  350 
Pyramidal  decussation,  204 

tracts,  177 


Rami  capsulares,  337 

Ranii'm  y   Cajal's    discoveries,    182, 

180,  440,  450 
Ranvier's  constrictions,  146 

nodes,  146 

Raphe,  209 

Red  blood  corpuscles,  20 
Red  nucleus,  230 
Reissner's  membrane,  46 
Eemak's  fibrous  layer,  108 

nerve-fibre,  148 

Rete  Malpighii,  33 

mucosum,  33 

testis,  370 

Reticular  cartilage,  67 

formation,  200 

Restiform  body,  200 
Retina,  445 

,  Blind  spot  of,  446 

,  Blood-vessels  of,  456 

,  Ganglion  cells  of,  448 

,  Lymphatics  of,  456 

Rhabdia  of  Kiihne,  92 

Rhodopsin  of  Kiihne,  453 

Rods  and  cones,  452 

Rollett's       secondary      substance, 

03 
Rosette  stage  in  nucleus,  13 
Rugse,  30S 


49S 


Elements  of  Histology. 


Rutherford's    scheme     of     ir.uscle 
contr.iction,  99 


Saccules,  -k52 

Saccus  endolvmphaticus,  461 

Saliva,  300 

Salivary  cells,  293 

•  glands,  2S6 

.  Blood-vessels  of.  297 

,  Ducts  of,  291 

.  Lobes  of,  290 

:  Lobules  of,  290 

,  Lnnphatics  of.  297 

,  Xenes  of.  297 

Sarcode  of  Dujardin,  .j 
Sarcoglia,  100 
Sareolemma,  91 
Sarcoplasma,  92 
Sarcoplasts,  101 
Sarcous  elements,  94 
Scala  tAiupaui,  465 

vestibuli,  335,  465 

Schultze's  protoplasm,  5 
Schwann's  cells.  5 
Sclerotic,  432 
Scrotum,  S7 
Sebaceous  follicles,  41S 
Semicircular  canals,  462 
Seminal  cells,  375 

tubules,  374 

Sensory  decussation,  207 

end-organs  in  muscle,  166 

in  tendon,  16S 

ganglion  cells,  197 

Septum  cistenise  lymphatiese.  45 
Serous  glands,  2S6,  299 

membranes,  122 

Sesamoid  cartilages,  f>*^ 
Sharpevs  perforating  fibres,  74 
Sheath"  of  Henle,  142 

of  Schwann,  145 

Simple  axis  cylinders,  153 

Ivmphatic  glands,  126 

Skin,  404 

-,  Blood-vessels  of,  421 

,  Lymphatics  of,  422 

.  Nerves  of,  423 

Solitarv  glands.  130 

lymph  follicles,  321 

Spaces  of  Foutana,  434 
Spermatoblasts,  377 
Spermatozoa,  37S 
Sphincter  pupillae,  437 
Sphincters,  SS 
Spinal  accessor^-,  203 

conl,  170  ! 

grey  matter,  191 


.Spinal  cord  white  matter,  186 
Spiral  fibre.  267 

tubule,  363 

Spireme,  convolution,  13 
Spleen,  3jl 

,  Capsule  of,  351 

,  L^Tiiphatics  of,  355 

,  Xerve-tibres  of,  242,  355 

.  Parenchyma  of,  352 

,  Pulp  o.^'353 

.  Red  blood  corpiLScles  of,  2S 

,  Trabecule  of,  352 

Spongioblast,  450 

Spongioplasm,  7 

Spong'y  bone  substance,  74 

Squamous  epithelial  ceils,  32 

Sternal  cartilage,  63 

Stigmata,  112 

Stomach,  310 

Stomata,  112,  121,  349 

Stratified  columnar  epithelium,  35 

pavement  epithelium,  32 

Stratum  adiposmn.  406 

cinereum,  231 

comeum,  33 

■  glomerulosum,  251 

granulosum,  34,  250 

lacunosum,  249 

lemnisci,  231 

liicidum,  33 

Malpighii,  33 

optieum,  232 

radiatum,  249 

zonale,  231 

Strife  acusticte   220 

Stria  vascularis,  468 

Stroma,  22 

Subarachnoidal  spaces,  121,  170 

tissue,  171 

Subcutaneous  lymphatics,  422 

tissue,  406 

Subdural  spaces,  121,  170 
Subendocardial  tissue,  105 
Subepithelial  endothelium  of   De- 

l)Ove,  51 
Subhyaloid  ceUs,  443 
Submaxillary  ganglion .  253 
Submucosa,  300 
Submucous  lymphatics,  121 
Subpericardial  nerve  branches,  107 

ti.ssue,  106 

Substantia  ferruginea,  225 

gelatinosa,  iS6 

nigra.  229 

Subvaginal  space,  457 
Sudoriferous  canal.  407 
Sulcus  hippocampi,  249 
spiralis,  467 

Superior  pedunculus  cerebelli,  22S 


Index. 


499 


Suprachoroiilal  tissue,  434 
.Suprarenal  bodies,  480 
Supravaj^iiial  space,  457 
Suspt'usory  ligament,  443 
Sweat  glan< Is,  407 
Sympathetic  system,  "258 
Synapsis,  ]9f> 
Synovial  cavities,  121 


Tactile  eurpuscles,  1-38,  423 

hairs,  417 

Tapetuni  nigrum,  43!>,  454 
Tarsal  plate,  424 

Taste  buds,  305 

cells,  305 

goblets,  305 

Teeth,  275 

cement,  279 

develoimient,  280 

pulp.  279 

Tegmental  cells,  305 
Tegmentum,  231 
Teichmann's  crystals,  23 
Tendon  cells,  49 

spindles,  167 

Temlons,  49 
Tendril  fibres,  243 
Tenoniau  capsule,  457 

space,  457 

Tensor  choroidete,  435 
Ternainal  bronchi,  347 
Testis,  372 
Thoracic  duct,  117 
Thymus  fullicles,  131 

■  gland,  131 

Thyroid  cartilage,  63 

gland,  484 

Tongue,  302 

,  Serous  glands  of,  304 

Tonsils,  129 

Touch-cells  of  Merkel,  161 

corpuscles  of  Merkel,  169 

Trabecule  carne*,  106 

of  lymphatics,  134 

of  sjileen,  352 

Trachea,  343 

Tracts  of  white  matter  in  cord,  17 
Tract  cells,  197 
Transitional  epithelium,  35 
Transverse  disc,  95 
Trapezoid  nucleus,  218 
Trapezium,  218,  226 
Tuba  Eustachii,  459 
Tubercle  of  Rolando,  202 
Tnberculuni  acusticum,  219 
Tubes  of  epididymis,  379 
Tunica  adnata,  372 


Tunica  albuginea,  37 

dartos,  88 

fibrosa.  .390 

prnpriii,  4i>9 

•  vaginalis,  372 

Tyson's  glands,  384 


Ureter,  371 
Urethra,  Female,  399 

,  Male,  383 

Urinary  tubules,  361 
Uterus,  395 
Utricle,  462 
Uvea,  437 


Vagina,  397 

Varicose  nerve-fibres,  147 

Vas  deferens,  381 

rectum,  378 

Vasa  etferentia,  379 
Vascularisation  of  cartilage,  75 
Vater's  corpu.scles,  155 
Veins,  110 

,  Intima  of,  110 

,  Media  of,  110 

of  the  bones,  110 

Veins  of  the  l)rain,  cord,  gravid 
uterus,  membranes,  and  retina, 
110 

,  Valves  of,  110 

Vena  axillaris,  azygos,  cava,  cru- 
ralis,  hepatica,  intima,  iliaca, 
mcsenterica,  jtoplitea,  I'enalis, 
spermatica,  and  umViilicalis,  110 

jugularis,  and  subclavia,  110 

Venae  rectie,  369 

stellatfce,  370 

vorticosse,  441 

Venous  radicles,  353 

sinuses,  353 

Ventricle,  Fourth,  211 
Ventricles,  106 
Ve.sicula;  seminales,  381 
Vestibulum  of  labyrinth,  460 
Virchow's  crystals,  23 
Visceial  pericardium,  105 

peritoneum,  333 

Visual  purple,  453 
Vitreous  body,  443 


Wandering  cells,  58 
Weigert's  method,  182 
White  blood  corpuscles,  23 


500 


Elements  of  Histology. 


White  commissure,  187 

fibrous  tissue,  40 

substance  of  brain,  237 

of  cord,  ISiJ 

of  Sclnvann,  145 

Wolffian  body,  374,  3S7 

Wreath  arrangement  of  nucleus,  14 


Yellow  elastir  cartilai 


Yellow  elastic  tissue.  00 


Zona  fasciculata,  487 

glomerulosa,  486 

pel  In  ei  da,  1,  388 

reticularis,  487 

vasculosa,  386 

Zonula  ciliaris,  443 
Zinnii,  443 


I'rintedbyC'AssKLL  &  Company.  LnnTED.  La  Belle  Sau\aye,  Louilon,  E.G. 


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